Combined distributed ranging sessions including common devices

ABSTRACT

Independent ranging sessions that are initiated by multiple initiating user equipments (UEs) are detected and combined into a single combined ranging session to reduce overhead. The independent ranging sessions may be determined to be nearby and concurrent when a UE detects a number of ranging cycles within a predetermined time. The UE may send messages to each initiator UE indicating that the ranging sessions should be combined and the initiator UEs will terminated initiating any further ranging sessions. Combined ranging session may be initiated by the UE and may include all of the participating UEs from the independent ranging sessions. The combined ranging session continues until it is determined that one or more UEs in the combined ranging session are not receiving ranging signals from other UEs.

BACKGROUND Background Field

The subject matter disclosed herein relates to wireless communicationssystems, and more particularly to methods and apparatuses for ranging orpositioning of user equipment in a distributed wireless communicationssystem.

Relevant Background

Obtaining accurate position information for user equipment, such ascellular telephones or other wireless communication devices, is becomingprevalent in the communications industry. For example, obtaining highlyaccurate locations of vehicles or pedestrians is essential forautonomous vehicle driving and pedestrian safety applications.

A common means to determine the location of a device is to use asatellite positioning system (SPS), such as the well-known GlobalPositioning Satellite (GPS) system or Global Navigation Satellite System(GNSS), which employ a number of satellites that are in orbit around theEarth. In certain scenarios, however, location determination signalsfrom an SPS may be unreliable or unavailable, e.g., during adverseweather conditions or in areas with poor satellite signal reception suchas tunnels or parking complexes. Moreover, position informationgenerated using SPS is prone to imprecision. For example, off-the-shelfGPS positioning devices have an accuracy of a few meters, which is notoptimal to ensure safe autonomous driving and navigation.

Coordinated or automated driving requires communications betweenvehicles, which may be direct or indirect, e.g., via an infrastructurecomponent such as a roadside unit (RSU). For vehicle safetyapplications, both positioning and ranging are important. For example,vehicle user equipments (UEs) may perform positioning and ranging usingsidelink signaling, e.g., broadcasting ranging signals for other vehicleUEs or pedestrian UEs to determine the relative location of thetransmitter. An accurate and timely knowledge of the relative locationsor ranges to nearby vehicles, enables automated vehicles to safelymaneuver and negotiate traffic conditions. Round trip time (RTT), forexample, is a technique commonly used for determining a range betweentransmitters. RTT is a two-way messaging technique in which the timebetween sending a ranging signal from a first device to receiving anacknowledgement (e.g., in the form of return ranging signal) from asecond device (minus processing delays) corresponds to the distance(range) between the two devices.

SUMMARY

Independent ranging sessions that are initiated by multiple initiatinguser equipments (UEs) are detected and combined into a single combinedranging session to reduce overhead. The independent ranging sessions maybe determined to be nearby and concurrent when a UE detects a number ofranging cycles within a predetermined time. The UE may send messages toeach initiator UE indicating that the ranging sessions should becombined and the initiator UEs will terminated initiating any furtherranging sessions. Combined ranging session may be initiated by the UEand may include all of the participating UEs from the independentranging sessions. The combined ranging session continues until it isdetermined that one or more UEs in the combined ranging session are notreceiving ranging signals from other UEs.

In one implementation, a method of ranging between user equipments (UEs)performed by a first UE, includes receiving initial messages to initiateseparate ranging sessions from a plurality of UEs; sending a message tothe plurality of UEs to combine the separate ranging sessions andindicating that the first UE will initiate the combined ranging session;and performing the combined ranging session with the plurality of UEs.

In one implementation, a first user equipment (UE) configured forranging between UEs, includes a wireless transceiver configured towirelessly communicate with entities in a wireless network; at least onememory; and at least one processor coupled to the wireless transceiverand the at least one memory, wherein the at least one processor isconfigured to: receive initial messages to initiate separate rangingsessions from a plurality of UEs; send a message to the plurality of UEsto combine the separate ranging sessions and indicating that the firstUE will initiate the combined ranging session; and perform the combinedranging session with the plurality of UEs.

In one implementation, a first user equipment (UE) configured forranging between UEs, the first UE includes means for receiving initialmessages to initiate separate ranging sessions from a plurality of UEs;means for sending a message to the plurality of UEs to combine theseparate ranging sessions and indicating that the first UE will initiatethe combined ranging session; and means for performing the combinedranging session with the plurality of UEs.

In one implementation, a non-transitory storage medium including programcode stored thereon, the program code is operable to configure at leastone processor in a first user equipment (UE) for ranging between UEs,the program code comprising instructions to: receive initial messages toinitiate separate ranging sessions from a plurality of UEs; send amessage to the plurality of UEs to combine the separate ranging sessionsand indicating that the first UE will initiate the combined rangingsession; and perform the combined ranging session with the plurality ofUEs.

In one implementation, a method of ranging between user equipments (UEs)performed by a first UE, includes sending an initial message to a secondUE to initiate a first ranging session; receiving a message from thesecond UE to combine the first ranging session with a second rangingsession initiated by a third UE and indicating that the second UE willinitiate a combined ranging session; and performing the combined rangingsession with the second UE.

In one implementation, a first user equipment (UE) configured forranging between UEs, includes a wireless transceiver configured towirelessly communicate with entities in a wireless network; at least onememory; and at least one processor coupled to the wireless transceiverand the at least one memory, wherein the at least one processor isconfigured to: send an initial message to a second UE to initiate afirst ranging session; receive a message from the second UE to combinethe first ranging session with a second ranging session initiated by athird UE and indicating that the second UE will initiate a combinedranging session; and perform the combined ranging session with thesecond UE.

In one implementation, a first user equipment (UE) configured forranging between UEs, the first UE includes means for sending an initialmessage to a second UE to initiate a first ranging session; means forreceiving a message from the second UE to combine the first rangingsession with a second ranging session initiated by a third UE andindicating that the second UE will initiate a combined ranging session;and means for performing the combined ranging session with the secondUE.

In one implementation, a non-transitory storage medium including programcode stored thereon, the program code is operable to configure at leastone processor in a first user equipment (UE) for ranging between UEs,the program code comprising instructions to: send an initial message toa second UE to initiate a first ranging session; receive a message fromthe second UE to combine the first ranging session with a second rangingsession initiated by a third UE and indicating that the second UE willinitiate a combined ranging session; and perform the combined rangingsession with the second UE.

BRIEF DESCRIPTION OF THE DRAWING

Non-limiting and non-exhaustive aspects are described with reference tothe following figures, wherein like reference numerals refer to likeparts throughout the various figures unless otherwise specified.

FIG. 1 illustrates a wireless communication system illustratingdistributed communications, including ranging signaling to supportmultiple ranging sessions and/or positioning.

FIG. 2 illustrates a signaling graph indicating the timing andfrequencies of various messages that may be sent and received by aninitiator UE and three responder UEs for a ranging or positioningsession.

FIG. 3A illustrates a system that includes number of UEs participatingin two independent ranging sessions that are separately initiated.

FIG. 3B is similar to FIG. 3A but illustrates the system in whichindependent ranging sessions are combined into a single combined rangingsession.

FIG. 4 illustrates a visibility map that may be generated fordetermining the number of ranging signals that are missed during acombined ranging session.

FIG. 5 illustrates a signaling flow for combining independent rangingsessions into a single ranging session.

FIG. 6 shows a schematic block diagram illustrating certain exemplaryfeatures of a UE configured for combining independent ranging sessionsinto a single ranging session.

FIG. 7 is a flow chart illustrating a method of ranging between UEs.

FIG. 8 is a flow chart illustrating a method of ranging between UEs.

DETAILED DESCRIPTION

A distributed approach may be used for ranging and positioning ofvehicles, roadside units (RSU), and pedestrian and may avoid the needfor a centralized base station to coordinate and relay communications.Such communications may be used, for example, for automated driving andvehicle safety applications. Communications used in a distributedapproach may be made directly, e.g., between vehicles, or betweenvehicles and a RSU or pedestrian. These communications may includemessages and information elements (IEs) with which a vehicle may provideinformation necessary for automated driving.

For example, for safe operation of autonomous vehicles, the relativelocations or ranges to other vehicles needs to be determined. Variousapproaches may be used to derive the relative positions betweenvehicles. For example, relative positions of vehicles may be derivedusing ranging signaling. Ranging signals are sometimes referred to asphysical ranging signals, positioning ranging signals, positioningreference signals, or physical referencing signals, and may becollectively referred to herein as PRS signals. PRS signals, forexample, may be broadcast by a user equipment (UE) in a vehicle,sometimes referred to as V-UE, and received by other V-UEs and/orinfrastructure, e.g., RSU, or UEs held by a pedestrian, using directcommunication systems, such as dedicated short-range communication(DSRC), cellular Vehicle-to-Everything (C-V2X) communication, and even5G New Radio (NR) communications. PRS signals are used to determine arange to the broadcasting vehicle, e.g., using one way ranging,round-trip-time (RTT) positioning operations, or other standardpositioning operations such as time of arrival (TOA), time difference ofarrival (TDOA) or observed time difference of arrival (OTDOA).

In a distributed system, an individual UE is able to range with respectto other UEs that are nearby using messages and positioning signals thatare transmitted directly to the other UEs. In an RTT-based rangingsession, for example, multiple messages and signals are transmitted andreceived by each UE. For example, an initial set of pre-ranging signalmessages (pre-PRS messages) are transmitted and received to request andaccept a ranging session, followed by broadcasting the ranging signals(PRS signals) for measurement, which is followed by a set ofpost-ranging signal messages (post-PRS messages) that exchangemeasurement payloads. For RTT-based ranging and positioning, forexample, the time of arrival (TOA) and time of departure (TOD)measurements of transmitted and received PRS signals may be provided inthe post-PRS messages and used by each UE pair to determine the rangebetween the UEs. The pre-PRS and post-PRS messages may be sent over alicensed spectrum to guarantee reliability, while the PRS signals may bebroadcast over an unlicensed spectrum (e.g., to enjoy a larger availablebandwidth in e.g., UNI-III spectrum). Ranging sessions in a distributedsystem, i.e., without infrastructure support to coordinate messaging,may result in multiple ranging sessions occurring simultaneously thatmay include overlapping sets of participating UEs. Each ranging sessionmay include multiple messages and ranging signals that are exchangedbetween the participating UEs and each ranging session may includemultiple participating UEs. Accordingly, where multiple ranging sessionsoccur simultaneously, the signaling overhead may become excessivelylarge and may undermine ranging and positioning of the UEs.

The distributed mechanism ensures a minimum overhead, but multiplenearby UEs may initiate separate ranging sessions independently of eachother. For example, without overhead communications to control rangingsessions, two UE may separately broadcast their own pre-PRS signals tothe same set of responder UEs resulting in two independent rangingsessions that include the same responder UEs and that occur at the sametime. The number of messages exchanged in each separate ranging sessionmay be large, particularly if there are a number of responder UEs.Further, some signaling, such as the PRS signals, may be broadcast overan unlicensed spectrum, which may delay transmissions due tolisten-before-transmit (LBT) procedures used with the unlicensedspectrum. Accordingly, a significant overhead may be present when thereare multiple overlapping ranging sessions. The overhead may undermineranging and positioning in the sessions, e.g., due to additional delaysin receiving signaling.

Accordingly, in an implementation, as discussed herein, independentranging sessions may be combined to a single ranging session therebyreducing the amount of signaling that must be exchanged between UEs. Forexample, a responder UE that receives multiple pre-PRS messages frommultiple initiator UEs for separate ranging sessions may send a messageto the initiator UEs indicating that the separate ranging sessionsshould be combined, and that the responder UE will initiate the combinedranging session. The responder UE then becomes an initiator UE bysending a pre-PRS message to initiate the combined ranging session. Uponreceipt of the message from the responder UE that the ranging sessionswill be combined, the original initiator UEs will stop initiatingranging sessions and will become responder UEs for the combined rangingsession.

FIG. 1 illustrates a wireless communication system 100 illustratingdistributed communications, including ranging signaling to supportmultiple ranging sessions and/or positioning, as described herein.Wireless communication system 100 illustrates a first vehicle 102 with afirst wireless device, e.g., V-UE 102, in wireless communications withanother V-UE 104, illustrated as a second vehicle. The V-UE 102 andV-UE104 may comprise, but are not limited to, an on-board unit (OBU), avehicle or subsystem thereof, or various other communication devices.The V-UEs 102 and 104 function and provide communications on behalf oftheir associated vehicles and, accordingly, may be sometimes referred toherein simply as vehicles 102 and 104 or UEs 102 and 104. The first UE102 and second UE 104, for example, may be two vehicles traveling on aroad along with other vehicles, not illustrated.

The wireless communication system 100 may use, e.g.,Vehicle-to-Everything (V2X) communication standard, in which informationis passed between a vehicle and other entities within the wirelesscommunication network. The V2X services include, e.g., services forVehicle-to-Vehicle (V2V), Vehicle-to-Pedestrian (V2P),Vehicle-to-Infrastructure (V2I), and Vehicle-to-Network (V2N). The V2Xstandard aims to develop autonomous or semi-autonomous driving systems,such as Advanced Driver Assistance System (ADAS), which helps driverswith critical decisions, such as lane changes, speed changes, overtakingspeeds, and may be used to assist in parking as discussed herein. Lowlatency communications are used in V2X and are therefore suitable forprecise relative positioning, e.g., using ranging signals, such as oneway ranging, RTT, TDOA, etc.

In general, there are two modes of operation for V2X services, asdefined in Third Generation Partnership Project (3GPP) TS 23.285. Onemode of operation uses direct wireless communications between V2Xentities, which may sometimes be referred to as sidelink communication.The other mode of operation uses network based wireless communicationbetween entities. The two modes of operation may be combined, or othermodes of operation may be used if desired.

The wireless communication system 100 may operate using direct orindirect wireless communications between the UE 102 and UE 104. Forexample, the wireless communication may be over, e.g., Proximity-basedServices (ProSe) Direction Communication (PC5) reference point asdefined in 3GPP TS 23.303, and may use wireless communications underIEEE 1609, Wireless Access in Vehicular Environments (WAVE), IntelligentTransport Systems (ITS), and IEEE 802.11p, on the ITS band of 5.9 GHz,or other wireless connections directly between entities. Thus, asillustrated, UE 102 and UE 104 may directly communicate using with aVehicle-to-Vehicle (V2V) communication link 103. UE 102 and UE 104 maysimilarly directly communicate with roadside unit (RSU) 110 viaVehicle-to-Infrastructure (V2I) communication links 107 and 109,respectively. The RSU 110 may include a backhaul connection to anetwork, illustrated by wired connection 111, but may via a wireless Uuinterface to a base station. The RSU 110, for example, may be astationary infrastructure entity, that may support V2X applications andthat can exchange messages with other entities supporting V2Xapplications. An RSU may be a logical entity that may combine V2Xapplication logic with the functionality of base stations in a RAN, suchas an eNB, ng-eNB, or eLTE (referred to as eNB-type RSU) or a gNB, or UE(referred to as UE-type RSU). The RSU 110 may be used for ranging withUEs 102, 104, or other UEs, and because the position of the RSU 110 maybe known precisely, the RSU 110 may be used as an anchor UE with which aposition of the UE 102, 104 or other UEs may be determined. The RSU 110may sometimes be referred to herein as UE 110. The UEs 102, 104 and UE110 may communicate with additional entities, such as additionalvehicles, RSUs or with a UE 112 held by pedestrian 114 using directcommunication links. For example, UE 102 may communicate with UE 112 viaV2V communication link 113, UE 104 may communicate with UE 112 via V2Vcommunication link 115, and UE 110 may communicate with UE 112 via V2Icommunication link 117.

During direct communications with one or more entities in the V2Xwireless communication system 100, each entity may provide V2Xinformation, such as an identifier for the V2X entity, as well as otherinformation in messages such as Common Awareness Messages (CAM) andDecentralized Notification Messages (DENM) or Basic Safety Message(BSM), which may be used for, e.g., ADAS or safety use cases.

In other implementations, UE 102 and UE 104 may indirectly communicatewith each other, e.g., through the RSU 110 via the V2I communicationlinks 107 and 109, respectively or through other network infrastructure(not shown), e.g., using cellular vehicle-to-everything (CV2X). Forexample, vehicles may communicate via a base station in a Radio AccessNetwork (RAN), such as an evolved Node B (eNB) or next generationevolved Node B (ng-eNB) in LTE wireless access and/or evolved LTE (eLTE)wireless access or a NR Node B (gNB) in Fifth Generation (5G) wirelessaccess.

UEs 102 and 104 may initiate and perform ranging/positioning sessions,including sending pre-PRS messages, broadcasting PRS, and sendingpost-PRS messages on links 103, 107, 109, 113 or 115, with which therange or relative positions between UEs 102 and 104 may be determined.The PRS broadcast by UEs 102 and 104 may be any signal suitable forranging, e.g., as defined for DSRC or C-V2X. The PRS may be broadcast onlicensed or unlicensed spectrum. For example, in some implementations,PRS may be broadcast on one or more Unlicensed National InformationInfrastructure (UNIT) radio bands including, for example, one or more ofthe UNII-1 radio band, the UNII-2A radio band, the UNII-2B radio band,or the UNII-3 radio band. When broadcasting on unlicensed spectrum,listen-before-transmit (LBT) protocols may be employed.

Where UEs 102 and 104 broadcast PRS in a V2V link 103, the range orrelative positions between UEs 102 and 104 may be determined directly.Where UE 102 and 104 broadcast PRS in V2I links 107 and 109 or via links113 and 115, the range or relative positions between UE 102 and UE 110or UE 112 and between UE 104 and UE 110 or UE 112 may be determineddirectly.

The direct wireless communications between the UE 102 and 104 and UE 110and UE 112, do not require any network infrastructure and enable lowlatency communications, which is advantageous for precise ranging orpositioning. Accordingly, such direct wireless communications may bedesirable for ranging over short distances, e.g., with nearby vehiclesor infrastructure.

The UEs, e.g., any of V-UE 102, V-UE 104, RSU 110, and UE 112, shown inFIG. 1, may be configured to perform ranging and/or positioningoperations, such as RTT-based ranging.

FIG. 2 illustrates, by way of example, a signaling graph 200 indicatingthe timing and frequencies of various messages that may be sent andreceived by an initiator UE (UEX) and three responder UEs (UEA, UEB, andUEC) for a ranging or positioning session. For example, FIG. 2illustrates capabilities messages 201 and an RTT-based ranging session202, during which a number of messages are sent between an initiator UEand responder UEs, including pre-PRS messages 204 to request and accepta ranging session, the PRS signals 208 for measurement, and post-PRSmessages 208 to exchange measurement payloads. Each set of pre-PRS 204,PRS 206, and post-PRS208 may be considered a single unit or PRS cycle.Each PRS cycle includes a pre-PRS message 204, PRS signal 206, andpost-PRS message 208, and may therefore be referred to herein as aranging session 202. The ranging sessions (PRS cycles) may be periodicwith a period T_r, and the capabilities messages may be periodic with aperiod T_c, where T_r>T_c. In FIG. 2, the signaling from the initiatorUEX is illustrated with white boxes that are labeled “X,” signaling froma first responder UEA is illustrated with gray boxes that are labeled an“A,” signaling from a second responder UEB is illustrated with hatchedboxes that are labeled with a “B,” and signaling from a third responderUEC are illustrated with block boxes that are labeled with a “C.” Thesignaling from the initiator UEX is the first box in each of the pre-PRSmessages 204, the PRS signals 206, and the post-PRS messages 208, and isfollowed by the responder UEs (UEA, UEB, and UEC).

As illustrated, the UEs, including the initiator UE and responder UEs,may broadcast capabilities messages 201. The capabilities messages arenot part of the ranging session but may include information that may beused by the initiator UE to initiate a ranging session with selectedUEs. For example, the capabilities message may be on the ITS spectrumand may include the UE ID, the ranging capability of the UE, the channelthat the UE is configured to use, MIMO (Multiple Input Multiple Output)capabilities, etc. The capabilities message may additionally indicatewhether the UE needs to determine its position or if its position isknown and it may serve as an anchor UE for positioning other UEs. Thecapabilities message may additionally indicate whether the UE is capableof combining ranging sessions or capable of allowing its initiatedranging session to be combined with another ranging session. It shouldbe understood that while FIG. 2 illustrates the capabilities messages201 as having the same order as the messages in the ranging session 202,the order may, in fact, differ.

The pre-PRS messages 204 (e.g., pre-ranging messages) are used by theUEs to request and acknowledge a ranging session. As illustrated, thepre-PRS messages 204 may be transmitted on a licensed spectrum toguarantee reliability. The pre-PRS messages 204 may be broadcast orunicast, e.g., with Radio Resource Control (RRC) connections. Theinitiator UEX broadcasts an initial pre-PRS message 204 (PrePRSRequest)to initiate the ranging session between the initiator UE and theresponder UEs and to provide information for the ranging session(illustrated with the white box labeled X). For example, the pre-PRSmessage 204 from the initiator UE, may include IDs for participatingUEs, i.e., the initiator and responder IDs. The pre-PRS request messagemay include a ranging session ID, the channel for the PRS broadcast bythe initiator UEX and responder UEs, the PRS broadcast time, the maximumlisten before transmit (LBT) time, etc. The pre-PRS request message fromthe initiator UEX for example may include a PRS ID that will be used bythe initiator UE, and in some implementations, the PRS ID to be used bythe responder UEs. If the PRS ID will be fixed over multiple PRSexchanges (e.g., for multiple units in the ranging session 202), theinitiator UE may include an ID associated with the current PRS exchange,e.g., a session ID. The initiator UE may determine when the PRS signals206 will be transmitted, which, for example, may be configured from anupper layer in the initiator UE. The initiator UE may indicate thetiming of the PRS by sending the time slot number nears to the desiredPRS transmission time. In some implementations, the time slot may besubject to local clock error. The initiator UE may further provide thetiming of PRS to be sent by the responder UEs, as well as a maximum LBTtime or other maximum predetermined delay for broadcasting the PRS. Theinitiator UE may further indicate the frequency that will be used tobroadcast the PRS signal 206 by the initiator UE and the responder UEs.For example, the frequency of PRS may be selected from an available setof total bandwidths or the frequency of PRS may be selected by sensingthe interference and choosing one or more channels whose averageinterference Reference Signal Receive Power (RSRP) is less than athreshold. The initiator UE may indicate the number of PRS cycles thatit will execute during the ranging session 202. The number of PRS cyclesmay be configured from an upper layer. The pre-PRS message for each PRScycle, for example, may indicate the current PRS cycle with respect tothe total PRS cycles requested, where the number of the current cycleincrements after completion of each cycle.

The initial pre-PRS request message from the initiator UE is receivedand decoded by the responder UEs, which are identified in the initialpre-PRS message. The responder UEs may send pre-PRS messages 204 inresponse (illustrated with gray, hatched, and black boxes labeled withA, B, C, respectively) which may acknowledge the pre-PRS requestmessage, which may additionally provide information for the rangingsession. For example, each responder UE may determine the timing of itsPRS signal 208, e.g., based on the PRS timing of the initiator UE plus adelay, which may be based on hardware constraints and the interferencelevel, and the number and order of responder UEs. For example, the delaymay be relatively low when the PRS processing time is small and ambientinterference is low and may be relatively high when the PRS processingtime is high and ambient interference is high. The responder UE mayindicate the determined time of its PRS by sending the time slot numbernears to the determined PRS transmission time. In some implementations,the time slot may be subject to local clock error. Each responder UE mayindicate the PRS ID that it will use or may indicate that it will usethe PRS ID that was indicated in the initial pre-PRS message. If the PRSID will be fixed over multiple PRS exchanges (e.g., multiple PRS cyclesin the ranging session 202), the responder UE may include the IDassociated with the current PRS exchange, e.g., a session ID, that wasreceived in the initial pre-PRS message from the initiator UE. Theresponder UEs may broadcast the pre-PRS messages 204, which may bereceived by the initiator UE (and other responder UEs). In someimplementations, each responder UE may transmit the pre-PRS message 204using unicast with RRC connection to the initiator UE.

The PRS signals 206 are exchanged by the participating UEs. Theinitiator UE and responder UEs know the expected timing and frequenciesof the PRS signals and know the PRS ID (and any session ID used with theexchanged) that is used to broadcast the PRS signals 206. The PRSsignals 206 may be, for example, a Quadrature Phase Shift Keying (QPSK)modulated pseudo-noise (PN) sequence and may include the ranging sessionID. The PRS signals 206 may be broadcast on an unlicensed spectrum,which may be subject to LBT constraints. In some implementations, whenusing the unlicensed spectrum, the initiator UEX may reserve thetransmission for responder UEs UEA, UEB, and UEC, so that the responderUEs may not need to perform LBT. For example, the initiator UEXbroadcasts its PRS signal 206 (white box labeled with X) at thedetermined time that was indicated in the initial pre-PRS message 204.In some implementations, the initiator UE broadcasts its PRS signal atthe determined time plus a random waiting time due to the LBTconstraints when the PRS signal is deployed in the unlicensed spectrum.In some implementations, the LBT may be a Category 2 LBT with a fixedwindow Clear Channel Assessment (CCA) or a Category 4 LBT with a varyingwindow CCA. The initiator UE uses the PRS signal that corresponds to thePRS ID and uses the frequency resources that were indicated in itsinitial pre-PRS message 204. The initiator UE stores the time instancethat the PRS signal is broadcast, and the responder UEs store the timeinstance that the PRS signal is received. In some implementations, thetime instances may be subject to local clock error.

Similar to the initiator UE, each responder UE broadcasts its PRS signal206 (illustrated with gray, hatched, and black boxes labeled with A, B,C, respectively) at the time and frequencies that were assigned in theinitial pre-PRS message 204 by the initiator UE. In someimplementations, each responder UE may broadcast its PRS signal at thedetermined time plus a random waiting time due to the LBT constraintswhen the PRS signal is deployed in the unlicensed spectrum. In someimplementations, the LBT may be a Category 2 LBT with a fixed window CCAor a Category 4 LBT with a varying window CCA. Each responder UE usesthe PRS signal that corresponds to the PRS ID that was indicated in itspre-PRS messages 204. Each responder UE stores the time instance thatits PRS signal is broadcast, and the initiator UE (and optionally otherresponder UEs) store the time instance that the PRS signal from eachresponder UE is received. In some implementations, the time instancesmay be subject to local clock error.

Thus, each UE records the time of departure (ToD) of its broadcast PRSsignal and measures the time of arrival (ToA) of the PRS signal receivedfrom the other UEs. The PRS signal may be any signal suitable forranging, e.g., as defined for DSRC or C-V2X, such as QPSK modulated PNsequence. The ToA and ToD resolution of the PRS signals increase with anincreased frequency bandwidth. In some implementations, the angle ofdeparture (AoD) and angle of arrival (AoA) of the broadcast and receivedPRS signals may also be measured. Broadcasting on an unlicensed spectrumis advantageous as a wider frequency band is available. For example, insome implementations, PRS may be broadcast on one or more UNIT radiobands including, for example, one or more of the UNII-1 radio band, theUNII-2A radio band, the UNII-2B radio band, or the UNII-3 radio band.

The post-PRS messages 208 are sent by each UE to exchange measurementpayloads. As illustrated, the post-PRS messages 208 may be transmittedon a licensed spectrum to guarantee reliability. In someimplementations, the post-PRS messages 208 may be broadcast or unicastwith RRC connection. The initiator UEX sends its post-PRS message 208(illustrated as the white box labeled with X) and indicates when itbroadcast the PRS signal 206 (ToD) and when the PRS signals from theresponder UEs were received (ToA). In some implementations, the ToA maybe computed as a relative time with respect to the ToD of its broadcastPRS signal, and the relative time may be provided. In someimplementations, the relative time may be approximated to the closestmultiple of time scale shared by the initiator UE and the responder UEs.In some implementations, the initiator UE may provide an indication ofits location in the post-PRS message 208, if known. For example, thelocation of the initiator UE may be the location at a specific time,such as the broadcast time of its PRS signal or the arrival time of thePRS signal from a responder UE. The post-PRS message 208 may furtherinclude the AoD of its PRS signal 206 and the AoA of the PRS signals 206received from the responder UEs, the orientation of initiator UE, abroadcast indicator of the PRS signal 206, a reception indicator of PRSfrom the responder UEs, as well as other related measurements, e.g.,including map information, the locations of reflectors with respect tothe UE, etc.

Similar to the initiator UE, each responder UEs sends its post-PRSsignal 208 (illustrated with gray, hatched, and black boxes labeled withA, B, C, respectively) to provide the measurement payloads. Eachresponder UE may indicate whether it received the PRS signal from theinitiator UE and may indicate when it broadcast the PRS signal 206 (ToD)and when the PRS signals from the initial UE (and optionally from otherresponder UEs) was received (ToA). In some implementations, the ToD maybe computed as a relative time with respect to the ToA of the PRS signalfrom the initiator UE (and optionally with respect to the ToA of the PRSfrom other responder UEs). In some implementations, the relative timemay be approximated to the closest multiple of time scale shared by theinitiator UE and the responder UE. In some implementations, theresponder UE may provide an indication of its location in the post-PRSmessage 208, if known. For example, the location of the responder UEprovided may be the location at a specific time, such as the arrivaltime of PRS signal from the initiator UE or the departure time of itsbroadcast PRS signal. The post-PRS message 208 may further include theAoD of its PRS signal 206 and the AoA of the PRS signals 206 receivedfrom the initiator UEX (and optionally received from the other responderUEs), the orientation of initiator UE, a broadcast indicator of the PRSsignal 206, a reception indicator of PRS from the responder UEs, as wellas other related measurements, e.g., including map information, thelocations of reflectors with respect to the UE, etc.

After receiving the post-PRS messages, the initiator UE may compute itsrange (and in some implementations its location), e.g., using a Kalmanfilter, and then may transmit the next cycle of pre-PRS messages at atime that is indicated by an upper layer or that is autonomouslydetermined by the initiator UE.

The time between the first pre-PRS message 204 and the last post-PRSmessage 208 may be the duration of the ranging session and may be, e.g.,100 msec. The duration of each broadcast PRS signals 206 may be, e.g.,47 μsec. In some implementations, multiple PRS cycles, e.g., multipleinstances of pre-PRS messages 204, PRS 206, and post-PRS messages 208,may be used together to provide higher accuracy.

Both the initiator UE and the responder UEs may determine the rangebetween itself and each other UE in the ranging session based on the ToDand the ToA of the broadcast PRS signals. For example, the RTT betweenany pair of UEs (which may be any pair of initiating and responder UEs)may be determined based on the ToD, and ToA, for the PRS, signals (wherei=1 for PRS broadcast from a first UE and i=2 for PRS broadcast by asecond UE), as the difference between the ToD₁ and ToA₂ minus thedifference between the ToA₁ and the ToD₂, e.g., as follows.RTT=(ToD ₁ −ToA ₂)−(ToA ₁ −ToD ₂)  eq. 1

The RTT value is the round-trip time for the signal, and thus, the range(distance) between the UE, and UE2 may be determined as RTT/2 c, where cis the speed of light.

If the position of one or more responder UEs is known, the range betweenthe initiator UE and the responder UEs may be used along with the knownposition of the one of the responder UE to determine the position of theother UE, and thus, the ranging session may be a positioning session.The responder UEs with known positions that may be used for positioningmay sometimes be referred to herein as anchor UEs. The positions ofanchor UEs may be provided to other UEs through messaging, e.g., in thepre-PRS messages or in the post-PRS messages. If the range to multipleanchor UEs is determined, the positions of the multiple anchor UEs maybe used in multilateration to determine the position of the initiator UE(or other responder UEs).

The angle measurements, e.g., AoD, and AoA, may be used, e.g., forassistance in positioning. By way of example, based on the range betweentwo UEs and a measured AoA, the relative positions of the two UEs may bedetermined. With the relative positions of the UEs determined, if theactual position of one of the UEs is known (which may be provided, e.g.,in the pre-PRS messages 204 or post-PRS messages 208), the actualposition of the other UE may be determined. If the position of two UEsare known by a third UE, the ranges between the third UE and each of theother two UEs will produce two possible positions for the third UE,which may be resolved based on AoD/AoA information. The AoD may beuseful if the resolution of the AoA is poor or incorrect, for example.AoD may be measured, e.g., based on a known orientation of the UE (forexample, determined by a magnetometer), and the direction of thetransmitted signal relative to the UE (e.g., relative to an antennaarray of the UE used for beamforming). The AoA may be measured based onthe phase difference of a received signal at different antenna elementsof an antenna array and the known orientation of the UE, for exampledetermined by a magnetometer). Additionally, geographic constraints maybe used to assist in positioning, for example, by constraining possiblepositions of a vehicle based on positions that are accessible to avehicle, such as a road.

As discussed above, due to the distributed mechanism for ranging, it ispossible that multiple UEs may initiate independent ranging sessionsthat include at least some of the same responder UEs at approximatelythe same time. For example, two initiating UEs may separately broadcasttheir own pre-PRS signals to the same set of responder UEs resulting intwo independent ranging sessions that include the same responder UEs andthat occur at the same time.

FIG. 3A, by way of example, illustrates a system 300 that includesnumber of UEs participating in two independent ranging sessions that areseparately initiated by UE1 302 and UE2 304, which may be pedestrianUEs, vehicle UEs, etc. The initiator UE1 302 and initiator UE2 304, forexample, may not be able to detect each other, e.g., due to distances,and may each initiate ranging sessions by sending pre-PRS messages(illustrated by arrows 303 and 305, respectively) to the responder UEsincluding UEA 310A, UEB 310B, and UEC 310C, sometimes collectivelyreferred to as UEs 310, which may be RSUs, pedestrian UEs, vehicle UEs,etc. The pre-PRS messages 303 and 305 may be broadcast or unicastmessages.

Two concurrent ranging sessions, which include the same set of responderUEs, as illustrated in FIG. 3A, will result in a significant overhead.For example, each PRS cycle in the ranging session initiated by UE1 302will include a UE1 pre-PRS message, UEA/UEB/UEC pre-PRS messages, UE1PRS signal, UEA/UEB/UEC PRS signals, UE1 post-PRS message, andUEA/UEB/UEC post-PRS messages, while the each PRS cycle in the otherranging session initiated by UE2 304 will include a UE2 pre-PRS message,UEA/UEB/UEC pre-PRS messages, UE2 PRS signal, UEA/UEB/UEC PRS signals,UE2 post-PRS message, and UEA/UEB/UEC post-PRS messages. The resultinglarge signaling overhead will undermine ranging and positioning of theinitiator UEs UE1 and UE2 because, for example, the PRS signals areconstrained by LBT procedures.

Accordingly, it is desirable to combine the two ranging sessions, e.g.,by changing the initiator UEs, e.g., from two initiator UEs (UE1 302 andUE2 304) to a single initiator UE, e.g., UEA 310A.

FIG. 3B, by way of example, illustrates a system 350 in whichindependent ranging sessions such as shown in FIG. 3A are combined intoa single ranging session. The system 350 is similar to system 300 shownin FIG. 3B with like designated elements being the same.

In FIG. 3B, after confirming the existence of multiple nearby rangingsessions, e.g., the ranging sessions initiated by UE1 302 and UE2 304 inFIG. 3A, the UEA 310A may combine the two ranging sessions into a singleranging session that includes both initiator UEs, e.g., UE1 302 and UE2304 and the responder UEs 310. As illustrated in FIG. 3B, the UEA 310A,which was a responder UE in both ranging sessions initiated by UE1 302and UE2 304 in FIG. 3A may serve as the initiator UE for the combinedranging session in FIG. 3B. The responder UE (e.g., UEA 310A) mayinitiate a new combined ranging session that includes the participantsfrom the separate ranging sessions (shown in FIG. 3A). For example, asillustrated in FIG. 3B, for example, the UEA 310A may send pre-PRSmessages (illustrated by arrows 353-1, 353-3, 353-B, 353-C (sometimescollectively referred to as pre-PRS messages 353)) to the responder UEsfor the new combined ranging session, e.g., the UE1 302, UE2 304, UEB310B, and UEC 310C. The pre-PRS messages 353 may be broadcast or unicastmessages.

The combined ranging session may then proceed with the UEA-310A servingas the initiator UE and UE1 302, UE2 304, UEB 310B, and UEC 310C servingas responder UEs. The combined ranging session may include the pre-PRSmessages, the PRS signals, and post-PRS messages, as discussed above.The post-PRS messages in the combined ranging sessions is broadcast sothat the original initiator UEs (UE1 302 and UE2 304) receive PRSmeasurement information from each responder UE to determine their rangesto the other new initiator UE (UEA-310A) and other responder UEs UEB310B, and UEC 310C, and in some implementations their positions, whileserving as responder UEs in the combined ranging session.

The initiator UE for the combined ranging session (e.g., UEA 310A) maycontinue to initiate combined ranging sessions for a predetermined timeor until participants in the combined ranging session are no longervisible to other participants. For example, in the combined rangingsession, the PRS signals from each participant (e.g., from initiatorUEA-310A and responder UE1 302, UE2 304, UEB 310B, and UEC 310C) shouldbe visible to each of the other. Once the PRS signals from participantsin the combined ranging session are not visible to other group members,e.g., more than N times, the combined ranging sessions may end and theoriginal initiator UEs 302 and 304 may begin initiating separate rangingsessions again. For example, the initiator UEA 310A for the combinedranging sessions may send a message (e.g., a V2X message) to theoriginal initiator UEs 302 and 304 indicating that the combined rangingsession should be separated, and UEA 310A will stop initiating newcombined ranging sessions and the original initiator UEs 302 and 304 canbegin initiating separate ranging sessions with appropriate responderUEs, which may be a different set of responder UEs than included in thecombined ranging sessions.

For example, in one implementation, the initiator UE for the combinedranging session (e.g., UEA 310A) may monitor which PRS signals fromother participants are visible (or missed) in each combined rangingsession. FIG. 4, by way of example, illustrates a visibility map 400that may be generated for determining the number of PRS signals that aremissed during each combined ranging session. As illustrated, eachparticipating UE in the combined ranging session may be included in thevisibility map 400, but in some implementations, only the originalinitiator UEs, e.g., UE1 and UE2, and the initiator UEA may beconsidered. Along each row, the visibility map 400 shows whether a UEreceives the PRS signal from another participating UE. For example, inrow 402, initiator UEA 310A is illustrated as receiving PRS signals fromUE1, UE2, and UEC, but not from UEB. Ideally, the visibility of PRSsignals is symmetric, i.e., if the PRS signal from UEB 310B is visibleto UEA 310A, then the PRS signal from UEA 310A should be visible to UEB310B.

The initiator UEA 310A may monitor multiple instances of combinedranging sessions and if the number missed PRS signals from otherparticipants in the combined ranging session exceeds a predeterminedthreshold N, the combined ranging session may be separated. In someimplementations, the threshold N may be used for all combined rangingsessions or the threshold N may be used for a discreet number ofprevious combined ranging sessions, e.g., N out of the last 10 combinedranging sessions. In some implementations, the initiator UEA 310A mayadditionally or alternatively monitor the post-PRS messages from eachresponder UE to determine the number of PRS signals that each responderUE has missed and may separate the combined ranging session if more thana threshold number of PRS signals are missed by the responder UEs. Inparticular, the initiator UEA 310A may consider the number of PRSsignals missed by the original initiator UEs, e.g., UE1 and UE2, whereasthe number of PRS signals missed by other responder UEs, e.g., UEB andUEC, may not be pertinent to whether the combined ranging session shouldbe separated. In another implementation, each responder UE, particularlythe original initiator UEs, e.g., UE1 and UE2, may separately monitorthe number of PRS signals that it has missed and may send a message tothe initiator UEA 310A indicating when more than a threshold number ofPRS signals have been missed. It should be noted that the PRS signalsfrom the original initiator UEs 302 and 304 may not be visible to eachother and, thus, it may not be desirable to consider missed PRS signalsbetween the original initiator UEs when determining whether a thresholdnumber of PRS signals have been missed.

The initiator UEA 310A may determine whether other participating UEs andparticularly the original initiator UEs, e.g., UE1 and UE2, received PRSsignals from other UEs based on their post-PRS messages or othermessages provided by the other UEs. Multiple visibility maps may becombined to determine if the total number of PRS signals for allcombined ranging sessions (or a discreet number of previous combinedranging sessions) is greater than a threshold. The initiator UEA 310A,for example, may monitor only the number of PRS signals missed by itselfor the number of PRS signals missed by a combination of participatingUEs, e.g., the original initiator UEs, e.g., UE1 and UE2initiator UE. Insome implementations, the initiator UEA 310A may considered only the PRSsignals missed by the original initiator UE1 and UE2.

FIG. 5 illustrates an example of a signaling flow 500 for combiningindependent ranging sessions into a single combined ranging session. TheUE entities 302, 304, 310A, 310B, and 310C, for example, may be V-UEs,RSU, and/or pedestrian UEs, such as UE 102, 104, 110, or 112 shown inFIG. 1 and discussed in FIGS. 3A and 3B and FIG. 4. The originalinitiator UEs may be UE1 302 and UE2 304 and original responder UEs maybe UEA 310A, UEB 310B, and UEC 310C. It should be understood thatadditional (or fewer) responder UEs may be present, which would involveadditional (or fewer) communications that are similar to that shown inFIG. 5. As illustrated, the communications between the UEs in FIG. 6 maybe direct communications between the entities and may not involveinfrastructure devices, such as base stations, to forward the messagesbetween the entities. It should be further understood that FIG. 5illustrates the signaling for combining independent ranging sessionsthat and that additional or other communications may be transmittedbetween one or more of the UEs shown in FIG. 5 in broadcast, unicast,multicast, or other sidelink signaling or through one or moreinfrastructure devices, such as RSU 110 or base stations.

At stage 1A, one or more ranging and/or positioning sessions areperformed with UE1 302 serving as the initiator UE and UEA 310A, UEB310Band UEC 310C serving as responder UEs. The participating UEs in theranging session of stage 1A may be identified/selected based oncapabilities messages, e.g., messages 201 shown in FIG. 2, in which theUEs provide their identities, ranging capabilities, configured channels,etc. The capabilities messages from responder UEs, e.g., UEA 310A,UEB310B and UEC 310C, may further indicate whether the UE is capable ofcombining ranging sessions, while the capability message from initiatorUE1 302 may indicate whether its initiated ranging session may becombined with another ranging session. The ranging session(s) of stage1A may not include UE2 304. As discussed, e.g., in FIG. 2, each rangingsession, for example, may include an initial pre-ranging message (suchas a pre-PRS message) from the initiator UE and responding pre-rangingmessages (such as pre-PRS messages) from the responder UEs. Each rangingsession may further include ranging signals (PRS signals) from theinitiator UE and the responding UEs, and post-ranging signals (post-PRSmessages) from the initiator UE and the responding UEs that carrymeasurement information for the ranging signals, as discussed in FIG. 2.The initiator UE may determine a range to each responder UE using themeasurement information. The responder UEs may similarly determineranges or timing information to the initiator UE and other responderUEs, which may be used for clock synchronization. The post-rangingmessages from anchor UEs may include location information with which theposition of UEs may be determined based on the location information anddetermined ranges to the anchor UEs.

At stage 1B, similar to stage 1A, one or more ranging and/or positioningsessions are performed with UE2 304 serving as the initiator UE and UEA310A, UEB310B and UEC 310C serving as responder UEs. The participatingUEs in the ranging session of stage 1B may be identified/selected basedon capabilities messages, e.g., messages 201 shown in FIG. 2, in whichthe UEs provide their identities, ranging capabilities, configuredchannels, etc. The capabilities messages from responder UEs, e.g., UEA310A, UEB310B and UEC 310C, may further indicate whether the UE iscapable of combining ranging sessions, while the capability message frominitiator UE2 304 may indicate whether its initiated ranging session maybe combined with another ranging session. The ranging session(s) ofstage 1B may not include UE1 302. The ranging and/or positioningsessions initiated by UE2 304 may be nearby and concurrent with theranging and/or positioning sessions of stage 1A.

At stage 2A, the UEA 310A determines to combine concurrent rangingsessions initiated by UEs 302 and 304. The UEA 310A, for example, maydetermine whether to combine concurrent ranging sessions if thecapabilities messages (e.g., at messages 201 in FIG. 2) from initiatorUE1 302 and UE2 304 indicate that ranging sessions initiated by them maybe combined with other ranging sessions. For example, UEA 310A mayconfirm the existence of multiple concurrent ranging sessions byreceiving pre-PRS messages from initiator UEs 302 and 304 in the rangingsessions in stage 1A and stage 1B. The UEA 310A may confirm theexistence of multiple independent ranging sessions based on the pre-PRSmessages in each ranging session, for example, which may list allparticipating UEs (including initiator UEs 302 and 304, respectively,and responder UEs 310). In some implementations, e.g., where the pre-PRSmessages 303 and 305 are unicast, the UEA 310A may confirm the existenceof multiple nearby ranging sessions by sensing a number of PRS cycles inboth ranging sessions in stage 1A and stage 1B within a time period. Forexample, the UEA 310A may sense whether the number of PRS signalsreceived from initiator UEs 302 and 304 is more than a predeterminednumber (X) within a time period, e.g., each second (X may be any valuebetween 0 and 10 given that PRS periodicity is 100 msec; 100 msec=1sec/10 PRS). In some implementations, the UEA 310A may sense the numberof pre-PRS messages and/or post-PRS messages received from initiator UEs302 and 304 in ranging sessions in stage 1A and stage 1B within a timeperiod. The post-PRS messages, for example, may include the time ofdeparture (ToD) of the broadcast PRS signals and may be used to assistin determining the number of PRS cycles from each initiator UE. In someembodiments, the UEA 310A may further sense the number of PRS broadcastfrom responding UEs, e.g., UEB 310B and UEC 310C within the time period.If the UEA 310A senses a number of PRS cycles from multiple rangingsessions within the time period, the UEA 310A may determine that theindependent ranging sessions from stages 1A and 1B are concurrent andshould be combined.

At stage 2B, one or more other responder UEs, illustrated as UEB 310Bmay also determine that the ranging sessions from stages 1A and 1B areto be combined as described in stage 2A.

At stage 3A, the UEA 310A may send a combine message (e.g., a V2Xmessage) to each of the initiator UEs 302 and 304 indicating that theranging sessions will be combined. The UEA 310A may indicate whether itcan serve as a positioning anchor (i.e., the location of UEA 310A isprecisely known) for positioning of the UEs 302 and 304. The UEA 310Amay further measure one or more power characteristics of the PRS signalsbroadcast by each of the initiator UEs 302 and 304 during the rangingsessions in stages 1A and 1B and may provide an indication of a powercharacteristic of the PRS signals from the initiator UEs 302 and 304 inthe combine message in stage 3A. For example, the UEA 310A may measurethe RSRP of PRS signals from both UE1 302 and UE2 304 and determine anaverage of the RSPR of the PRS signals. The UEA 310A may include theaverage RSRP of the PRS signals from UE1 302 and UE2 304 in the combinemessage.

At stage 3B, if the UEB 310B determined to combine the ranging sessionsin stage 2B, the UEB 310B may also send a combine message (e.g., a V2Xmessage) to each of the initiator UEs 302 and 304 indicating that theranging sessions will be combined and may provide an indication ofwhether UEB 310B may serve as a positioning anchor and an indication ofa measured power characteristic of the PRS signals, such as average RSRPof the PRS signals from UE1 302 and UE2 304 measured by UEB 310B.

At stages 4A and 4B, the initiator UE1 302 and initiator UE 304,respectively, may select an initiator UE for the combined rangingsessions and stop initiating independent ranging sessions. Thus, uponreception of the message from the UEA 310A to combine the rangingsessions, the two initiator UEs, e.g., UE1 302 and UE2 304, stopinitiating new ranging sessions, i.e., any subsequent initiation ofranging sessions by the two initiator UEs, e.g., UE1 302 and UE2 304, issuspended. The initiator UEs 302 and 304 wait to become responder UEs ina combined ranging session and select the initiator UE for the combinedranging session. For example, if only one responder UE (e.g., UEA 310A)sends a combine message, the UEs 302 and 304 may select the soleresponder UE. If the initiator UEs 302 and 304 receive combine messagesfrom more than one responder UE indicating that their ranging sessionswill be combined, e.g., in stages 3A and 3B, then the initiator UEs 302and 304 may determine which responder UE will serve as the new initiatorUE in the combined ranging session based on criteria such as the anchorstatus and power characteristics provided in the combine messages fromeach responder UE. For example, a responder UE with an ability to serveas an anchor point for positioning may be given priority over aresponder UE that cannot serve as an anchor point, and/or a responder UEwith a high average RSRP may be given priority over a responder UE witha low average RSRP. In some implementations, for example, the initiatorUEs 302 and 304 may determine which responder UE will be the newinitiator UE based on a combination of criteria, which may be ordered,such as: anchor with high average RSRP before anchor with low averageRSRP before non-anchor with high average RSRP before non-anchor with lowaverage RSRP. Other criteria, combinations of criteria, or orders may beused if desired.

At stage 5, each initiator UE 302 and 304 provide a responding combinemessage (e.g., a V2X message) to the selected responder UE (e.g., UEA310A in FIG. 5) indicating that it will be a responder UE and provide anindication that the responder UE is to initiate the combined rangingsession. A responder UE that sent a combine message to the initiator UEs302 and 304 may initiate the combined ranging or positioning sessions ifit receives a responding message from the initiator UEs 302 and 304.

At stage 6, UEA 310A initiates one or more combined ranging orpositioning sessions that includes the original initiator UEs, i.e., UE1302 and UE2 304, as responder UEs along with UEB 310B and UEC 310C. Thecombined ranging session(s) may be similar to the independent rangingsessions of stages 1A and 1B, but with UEA 310A initiating the rangingsessions and the previously initiator UEs (UE1 302 and UE2 304) servingas responder UEs. As discussed in, e.g., in FIG. 2, each rangingsession, for example, may include an initial pre-ranging message (suchas a pre-PRS message) from the initiator UE and responding pre-rangingmessages (such as pre-PRS messages) from the responder UEs. Each rangingsession may further include ranging signals (PRS signals) from theinitiator UE and the responding UEs, and post-ranging signals (post-PRSmessages) from the initiator UE and the responding UEs that carrymeasurement information for the ranging signals, as discussed in FIG. 2.The post-ranging messages from anchor UEs may include locationinformation with which the position of UEs may be determined based onthe location information and determined ranges to the anchor UEs. Thepost-PRS messages in the combined ranging sessions is broadcast so thatthe previously initiator UEs (UE1 302 and UE2 304) receive PRSmeasurement information from each responder UE to determine their rangesto the other new initiator UE (UEA-310A) and other responder UEs UEB310B, and UEC 310C, and in some implementations their positions, whileserving as responder UEs in the combined ranging session(s), asdiscussed above. The UEA 310A, UEB 310B, and UEC 310C may similarlydetermine ranges to participating UEs or timing information, which maybe used for clock synchronization.

At stage 7A, the initiator UEA 310A may determine whether to separatethe combined ranging sessions of stage 6. In some implementations,illustrated by optional stage 7B, other UEs may determine whether toseparate the combined ranging sessions of stage 6. It should beunderstood that while FIG. 5 illustrates stages 7A and 7B as beingperformed after stage 6, stages 7A and 7B in fact would be performed atthe same time as the combined ranging sessions of stage 6. In stage 7A,for example, the initiator UEA 310A for the combined ranging sessionsmay continue to initiate combined ranging sessions for a predeterminedtime or until participants in the combined ranging session are no longervisible to other participants. For example, the initiator UEA 310A, forexample, may monitor which PRS signals from other participants that arevisible (or missed) in each combined ranging session, as discussed abovein reference to FIG. 4. The initiator UEA 310A may monitor multiplecombined ranging session and if the number PRS signals from otherparticipants in the combined ranging session exceeds a predeterminedthreshold N, the combined ranging session may be separated. In someimplementations, the threshold N may be used for all combined rangingsessions or the threshold N may be used for a discreet number ofprevious combined ranging sessions, e.g., N out of the last 10 combinedranging sessions. In some implementations, the initiator UEA 310A mayadditionally or alternatively monitor the post-PRS messages from eachresponder UE to determine the number of PRS signals that each responderUE has missed and may separate the combined ranging session if more thana threshold number of PRS signals are missed by the responder UEs. Inanother implementation, each responder UE may separately monitor thenumber of PRS signals that it has missed (e.g., as illustrated by stage7B) and may send a message to the initiator UEA 310A indicating whenmore than a threshold number of PRS signals have been missed. Theinitiator UEA 310A may determine whether other participating UEsreceived PRS signals based on their post-PRS messages or other messagesprovided by the other UEs. The initiator UEA 310A, for example, maymonitor only the number of PRS signals missed by itself or the number ofPRS signals missed by a combination of participating UEs (which mayinclude or exclude the original initiator UE1 and UE2. In someimplementations, the initiator UEA 310A may considered only the PRSsignals missed by the original initiator UE1 and UE2.

At stage 8, once the UEA 310A determines that the combined rangingsessions should be separated, the UEA 310A sends a separate message(e.g., a V2X message) to the original initiator UEs 302 and 304indicating that the combined ranging session should be separated andstops initiating the combined ranging session.

At stages 9A and 9B, the original initiator UEs 302 and 304 begininitiating separate ranging sessions with appropriate responder UEs,which may be the same or a different set of responder UEs than includedin the combined ranging sessions.

Thus, the decision of merging and separating ranging sessions may beperformed autonomously and executed without the assistance of acentralized network. Multiple nearby ranging sessions may be combined toreduce the signaling overhead and may result in increased accuracy ofthe ranging between inter-group UEs and may be separated when thebenefits of the combined ranging session decrease or are lost.

FIG. 6 shows a schematic block diagram illustrating certain exemplaryfeatures of a user equipment (UE) 600, which may be UE in vehicles 102or 104, an RSU 110, or UE 112 held by a pedestrian 114, as illustratedin FIG. 1, or any UE illustrated in FIGS. 3A, 3B, 4, or 5. The UE 600may be configured to act as a responder UE, e.g., responder UEA 310A, oras an initiator UE, e.g., initiator UE1 302, where multiple independentand concurrent ranging sessions are combined into a single combinedranging session, as discussed herein. If the UE 600 is a V-UE, it may beconfigured to control the automated driving of a vehicle, e.g., vehicle102. For example, the UE 600 may include a vehicle interface 605 withwhich commands are provided to the vehicle for automated driving andsensory input, including speed and acceleration, may be provided fromthe vehicle to UE 600. The UE 600 may, for example, include one or moreprocessors 602, memory 604, an inertial measurement unit (IMU) 607 thatmay include, e.g., an accelerometer, gyroscope, magnetometers, etc.,which may be used to detect orientation with respect to a global orlocal reference frame and the motion or one or more motioncharacteristics of the vehicle, a satellite positioning system (SPS)receiver 609 to determine, e.g., a GPS position, and an externalinterface including, e.g., a Wireless Wide Area Network (WWAN)transceiver 610, and a Wireless Local Area Network (WLAN) transceiver614, which may be operatively coupled with one or more connections 606(e.g., buses, lines, fibers, links, etc.) to non-transitory computerreadable medium 620 and memory 604. The UE 600 may further includeadditional items, which are not shown, such as a user interface that mayinclude e.g., a display, a keypad or other input device, such as virtualkeypad on the display, through which a user may interface with the userdevice. In certain example implementations, all or part of UE 600 maytake the form of a chipset, and/or the like.

Transceiver 610 may be, e.g., a cellular transceiver, that is configuredto transmit and receive direct communications in the wireless network,as illustrated in FIG. 1. The transceiver 610 may include a transmitter611 enabled to transmit one or more signals over one or more types ofwireless communication networks and a receiver 612 to receive one ormore signals transmitted over the one or more types of wirelesscommunication networks. Transceiver 614 may be, e.g., a short-rangetransceiver, and may be configured to transmit and receive directcommunications in the wireless network, as illustrated in FIG. 1. Thetransceiver 614 may include a transmitter 615 enabled to transmit one ormore signals, including ranging signals (PRS signals) and pre-ranging(pre-PRS) and post-ranging (post-PRS) messages, and combine and separatemessages, over one or more types of wireless communication networks anda receiver 616 to receive one or more signals, e.g., including PRS andpre-PRS and post-PRS messages, combine and separate messages,transmitted over the one or more types of wireless communicationnetworks. The transceivers 610 and 614 enable the UE 600 to communicatewith transportation entities using D2D communication links, such asDSRC, C-V2X, or 5G NR.

In some embodiments, UE 600 may include antenna 609, which may beinternal or external. The antenna 609 may be used to transmit and/orreceive signals processed by transceiver 610 and/or transceiver 614. Insome embodiments, antenna 609 may be coupled to transceiver 610 and/ortransceiver 614. In some embodiments, measurements of signals received(transmitted) by UE 600 may be performed at the point of connection ofthe antenna 609 and transceiver 610 and/or transceiver 614. For example,the measurement point of reference for received (transmitted) RF signalmeasurements may be an input (output) terminal of the receivers 612, 616(transmitters 611, 615) and an output (input) terminal of the antenna609. In a UE 600 with multiple antennas 609 or antenna arrays, theantenna connector may be viewed as a virtual point representing theaggregate output (input) of multiple antennas. The phase difference ofreceived signals at multiple antennas or antenna array may be used todetermine the AoA of the signal with respect to the antenna array, whichmay be converted to a local or global reference frame based on a knownorientation of the UE 600, e.g., based on the orientation of the UE 600to the global or local reference frame as measured by the IMU 607.

The one or more processors 602 may be implemented using a combination ofhardware, firmware, and software. For example, the one or moreprocessors 602 may be configured to perform the functions discussedherein by implementing one or more instructions or program code 608 on anon-transitory computer readable medium, such as medium 620 and/ormemory 604. In some embodiments, the one or more processors 602 mayrepresent one or more circuits configurable to perform at least aportion of a data signal computing procedure or process related to theoperation of UE 600.

The medium 620 and/or memory 604 may store instructions or program code608 that contain executable code or software instructions that whenexecuted by the one or more processors 602 cause the one or moreprocessors 602 to operate as a special purpose computer programmed toperform the techniques disclosed herein. As illustrated in UE 600, themedium 620 and/or memory 604 may include one or more components ormodules that may be implemented by the one or more processors 602 toperform the methodologies described herein. While the components ormodules are illustrated as software in medium 620 that is executable bythe one or more processors 602, it should be understood that thecomponents or modules may be stored in memory 604 or may be dedicatedhardware either in the one or more processors 602 or off the processors.

A number of software modules and data tables may reside in the medium620 and/or memory 604 and be utilized by the one or more processors 602in order to manage both communications and the functionality describedherein. It should be appreciated that the organization of the contentsof the medium 620 and/or memory 604 as shown in UE 600 is merelyexemplary, and as such the functionality of the modules and/or datastructures may be combined, separated, and/or be structured in differentways depending upon the implementation of the UE 600.

The medium 620 and/or memory 604 may include a pre-PRS message module622 that when implemented by the one or more processors 602 configuresthe one or more processors 602 to generate and transmit or receivepre-ranging messages, such as pre-PRS messages, via the transceiver 614,e.g., to initiate a ranging session or to accept a ranging session. Thepre-PRS messages may be broadcast, multicast, or unicast (with RRCconnection). In some implementations, the PRS messages may betransmitted and received over a licensed spectrum. The pre-PRS messagemay be an initiating pre-PRS message to initiate a ranging session or aresponding pre-PRS message to acknowledge an initiating pre-PRS message.The pre-PRS messages may include identifiers for the initiator UE andone or more responder UEs. The participating UEs may be determined,e.g., from capabilities messages received by the UE 600 or frommonitoring multiple concurrent ranging sessions and identifying theparticipating UEs from the concurrent ranging sessions. The pre-PRSmessages may further include ranging signal properties to be used in aranging session and may include position information for the UE 600. Forexample, the pre-PRS message may include an identifier for the rangingsignal and timing information (e.g., time slot number) of the rangingsignal and frequency that will be used to broadcast the ranging signal.The frequency, for example, may be selected from an available set ofbandwidths, and may be selected by sensing interference and choosing achannel with an average interference RSRP that is less than a threshold.In some implementations, an initiating pre-PRS message may include anindication of the number of PRS cycles requested and the current PRScycle.

The medium 620 and/or memory 604 may include a PRS module 624 that whenimplemented by the one or more processors 602 configures the one or moreprocessors 602 to broadcast and receive a ranging signal to and fromother UEs in the ranging session, via the transceiver 614, as discussedherein. The ranging signal, for example, may be a PRS signal asdiscussed herein. The ranging signal may be broadcast at the determinedtime and with the identifier and at the frequencies indicated over thepre-PRS message. The ranging signal may be broadcast and received overunlicensed spectrum and may be broadcast pursuant to category 2 orcategory 4 LBT constraints. The one or more processors 602, for example,may be configured to measure the ToD of broadcast ranging signals andthe ToA of received ranging signals, and may be configured to measurethe AoD of broadcast ranging signals and the AoA of received rangingsignals.

The medium 620 and/or memory 604 may include a post-PRS message module626 that when implemented by the one or more processors 602 configuresthe one or more processors 602 to send and receive post-ranging messagesto and from other UEs in the ranging session, via the transceiver 614,as discussed herein. The post-PRS messages that may include, e.g., anindication of the ToD, and in some implementations the AoD, of thebroadcast ranging signals and an indication of the ToA, and in someimplementations the AoA, of the received ranging signals. In someimplementation, the indication of the ToD and ToA may be a differencebetween the ToD and ToA. In some implementations, the post-PRS messagesmay include an indication of the position of the UE.

The medium 620 and/or memory 604 may include a ranging/positioningmodule 628 that when implemented by the one or more processors 602configures the one or more processors 602 to determine a range toanother UE based on the ToD and ToA of broadcast and received rangingsignals as measured by the UE 600 and received in the post-PRS messagesfrom other UEs. The processor 602 may be further configured to determinea position of the UE 600, e.g., based on one or more ranges tobroadcasting UEs and their location information using multilateration orother appropriate techniques discussed herein. For example, the one ormore processors 602 may implement a Kalman filter or Extended Kalmanfilter to determine the range to other UEs and/or position of the UE600.

The medium 620 and/or memory 604 may include a combine sessions module630 that when implemented by the one or more processors 602 configuresthe one or more processors 602 to confirm the existence of independentconcurrent ranging sessions initiated by different initiator UEs. Theone or more processors 602 may be configured to determine the existenceof independent concurrent ranging sessions based on the pre-PRS messagesfor each ranging session, which may list all participating UEs includingdifferent initiator UEs. In some implementations, the one or moreprocessors 602 may be configured to determine the existence ofindependent concurrent ranging sessions by sensing whether the number ofPRS cycles in both ranging sessions exceed a threshold within a timeperiod. The number of PRS cycles may be determined by monitoring thenumber of PRS signal broadcasts or post-PRS messages, etc. If the numberof PRS cycles from multiple ranging sessions exceeds the thresholdwithin the time period, the independent ranging sessions may beconsidered concurrent and may be determined to be combined. The one ormore processors 602 may be configured to send a combine message, via thetransceiver 614, to the initiator UEs in each ranging session indicatingthat the ranging sessions should be combined, and that the UE 600 mayinitiate the combined ranging session, or to receive a combine messagefrom another UE, if the UE 600 is an initiator UE. The combine messagemay include an indication of whether the position of the UE is known,and thus, the UE may serve as a positioning anchor. The one or moreprocessors 602 may be further configured to measure one or more powercharacteristics, e.g., signal strength characteristics such as RSPR, ofthe ranging signals broadcast by the initiator UEs in each rangingsession. The signal strength characteristics determined by the one ormore processors 602 may be an average or other combination of themeasured power characteristics for the multiple ranging sessions. Thecombine message may provide an indication of a signal strengthcharacteristic of the ranging signals from the initiator UEs. The one ormore processors 602 may be further configured to receive, viatransceiver 614, a response message from the initiator UEs indicatingthat initiator UEs accept the combining of the ranging sessions and thatthe UE 600 is to initiate the combined ranging session. The one or moreprocessors 602 may be configured to initiate a combined ranging session,e.g., by sending an initial pre-PRS message that includes all of theparticipating UEs from the independent ranging sessions. The one or moreprocessors 602 may be further configured to select an initiator UE for acombined ranging session if multiple UEs send a combine message to theUE 600, where the selection may be based on whether ability to serve asan anchor point for positioning and signal strength characteristics. Theone or more processors 602 may be further configured to send, viatransceiver 614, a response message to the other UE indicating that UE600 accept the combining of the ranging sessions and that the other UEis selected to initiate the combined ranging session. The one or moreprocessors 602 may be further configured to send or receive, viatransceiver 614, in capabilities messages (such as illustrated bymessages 201 of FIG. 2), an indication of the availability of combiningranging sessions.

The medium 620 and/or memory 604 may include a separate sessions module632 that when implemented by the one or more processors 602 configuresthe one or more processors 602 to determine whether to separate thecombined ranging sessions. The one or more processors 602 may beconfigured to determine the number of ranging signals broadcast by oneor more UEs that are not received by one or more UEs in the combinedranging session and if the number is greater than a threshold. The oneor more processors 602 may be configured to sending a separate message,via the transceiver 614, to the previously initiator UEs indicating thatthe combined ranging session will be terminated and that the UEs shouldinitiate independent ranging sessions. Where the UE 600 is one of theoriginally initiator UEs, the one or more processor 602 may be furtherconfigured to receive a message, via the transceiver 614, indicatingthat a combined ranging session will be terminated, and that the UE 600should initiate independent ranging sessions.

The methodologies described herein may be implemented by various meansdepending upon the application. For example, these methodologies may beimplemented in hardware, firmware, software, or any combination thereof.For a hardware implementation, the one or more processors 602 may beimplemented within one or more application specific integrated circuits(ASICs), digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), processors, controllers, micro-controllers,microprocessors, electronic devices, other electronic units designed toperform the functions described herein, or a combination thereof. Theone or more processors 602 may be a general-purpose computer that onceprogrammed to perform particular operations pursuant to instructionsfrom program software as described herein operates as a special purposecomputer programmed to perform the techniques disclosed herein.

For a firmware and/or software implementation, the methodologies may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. Any machine readable mediumtangibly embodying instructions may be used in implementing themethodologies described herein. For example, software codes may bestored in a non-transitory computer readable medium 620 or memory 604that is connected to and executed by the one or more processors 602.Memory may be implemented within the one or more processors or externalto the one or more processors. As used herein the term “memory” refersto any type of long term, short term, volatile, nonvolatile, or othermemory and is not to be limited to any particular type of memory ornumber of memories, or type of media upon which memory is stored.

If implemented in firmware and/or software, the functions may be storedas one or more instructions or program code 608 on a non-transitorycomputer readable medium, such as medium 620 and/or memory 604. Examplesinclude computer readable media encoded with a data structure andcomputer readable media encoded with a computer program 608. Forexample, the non-transitory computer readable medium including programcode 608 stored thereon may include program code 608 to supportcombining multiple independent ranging sessions into a single combinedranging session, in a manner consistent with disclosed embodiments.Non-transitory computer readable medium 620 includes physical computerstorage media. A storage medium may be any available medium that can beaccessed by a computer. By way of example, and not limitation, suchnon-transitory computer readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to storedesired program code 608 in the form of instructions or data structuresand that can be accessed by a computer; disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer readable media.

In addition to storage on computer readable medium 620, instructionsand/or data may be provided as signals on transmission media included ina communication apparatus. For example, a communication apparatus mayinclude a transceiver 610 having signals indicative of instructions anddata. The instructions and data are configured to cause one or moreprocessors to implement the functions outlined in the claims. That is,the communication apparatus includes transmission media with signalsindicative of information to perform disclosed functions.

Memory 604 may represent any data storage mechanism. Memory 604 mayinclude, for example, a primary memory and/or a secondary memory.Primary memory may include, for example, a random-access memory, readonly memory, etc. While illustrated in this example as being separatefrom one or more processors 602, it should be understood that all orpart of a primary memory may be provided within or otherwiseco-located/coupled with the one or more processors 602. Secondary memorymay include, for example, the same or similar type of memory as primarymemory and/or one or more data storage devices or systems, such as, forexample, a disk drive, an optical disc drive, a tape drive, asolid-state memory drive, etc.

In certain implementations, secondary memory may be operativelyreceptive of, or otherwise configurable to couple to a non-transitorycomputer readable medium 620. As such, in certain exampleimplementations, the methods and/or apparatuses presented herein maytake the form in whole or part of a computer readable medium 620 thatmay include computer implementable code 608 stored thereon, which ifexecuted by one or more processors 602 may be operatively enabled toperform all or portions of the example operations as described herein.Computer readable medium 620 may be a part of memory 604.

FIG. 7 is a flow chart 700 illustrating a method of ranging between UEsperformed by a first UE, such as UEA 310A.

At block 702, the first UE receives initial messages to initiateseparate ranging sessions from a plurality of UEs, such as discussed atstages 1A, and 1B of FIG. 5. A means for receiving initial messages toinitiate separate ranging sessions from a plurality of UEs may be, e.g.,the transceiver 614 and the one or more processors 602 with dedicatedhardware or implementing executable code or software instructions inmemory 604 and/or medium 620, such as the pre-PRS message module 622.

At block 704, the first UE sends a message to the plurality of UEs tocombine the separate ranging sessions and indicating that the first UEwill initiate the combined ranging session, such as discussed at stage3A of FIG. 5. The first UE and the plurality of UEs, for example, mayeach be one of a vehicle-based UE, a pedestrian based UE, or a roadsideunit. A means for sending a message to the plurality of UEs to combinethe separate ranging sessions and indicating that the first UE willinitiate the combined ranging session may be, e.g., the transceiver 614and the one or more processors 602 with dedicated hardware orimplementing executable code or software instructions in memory 604and/or medium 620, such as the combine sessions module 630.

At block 706, the first UE performs performing the combined rangingsession with the plurality of UEs, such as discussed at stage 6 of FIG.5. A means for performing the combined ranging session with theplurality of UEs may be, e.g., the transceiver 614 and the one or moreprocessors 602 with dedicated hardware or implementing executable codeor software instructions in memory 604 and/or medium 620, such as thepre-PRS message module 622, PRS module 624, post-PRS message module 626,and ranging/positioning module 628.

In one implementation, the first UE may determine that the separateranging sessions are concurrent before sending the message to theplurality of UEs to combine the separate ranging sessions, e.g., asdiscussed at stage 2A of FIG. 5. A means for determining that theseparate ranging sessions are concurrent before sending the message tothe plurality of UEs to combine the separate ranging sessions may be,e.g., the transceiver 614 and the one or more processors 602 withdedicated hardware or implementing executable code or softwareinstructions in memory 604 and/or medium 620, such as the combinesessions module 630.

In one implementation, the first UE may determine that the plurality ofUEs initiate separate ranging sessions more than a predetermined numberof times before sending the message to the plurality of UEs to combinethe separate ranging sessions, e.g., as discussed at stage 2A of FIG. 5.A means for determining that the plurality of UEs initiate separateranging sessions more than a predetermined number of times beforesending the message to the plurality of UEs to combine the separateranging sessions may be, e.g., the transceiver 614 and the one or moreprocessors 602 with dedicated hardware or implementing executable codeor software instructions in memory 604 and/or medium 620, such as thecombine sessions module 630.

In one implementation, the first UE may send an initial message to theplurality of UEs to initiate the combined ranging session to theplurality of UEs, e.g., as discussed at stage 6 of FIG. 5. A means forsending an initial message to the plurality of UEs to initiate thecombined ranging session to the plurality of UEs may be, e.g., thetransceiver 614 and the one or more processors 602 with dedicatedhardware or implementing executable code or software instructions inmemory 604 and/or medium 620, such as the pre-PRS message module 622.For example, the first UE may receive response messages from theplurality of UEs indicating that each UE in the plurality of UEs acceptsthat the first UE will initiate the combined ranging session beforesending the initial message to initiate the combined ranging session tothe plurality of UEs, e.g., as discussed at stage 5 of FIG. 5. A meansfor receiving response messages from the plurality of UEs indicatingthat each UE in the plurality of UEs accepts that the first UE willinitiate the combined ranging session before sending the initial messageto initiate the combined ranging session to the plurality of UEs may be,e.g., the transceiver 614 and the one or more processors 602 withdedicated hardware or implementing executable code or softwareinstructions in memory 604 and/or medium 620, such as the combinesessions module 630.

In another implementation, the first UE may perform the combined rangingsession with the plurality of UEs by receiving an initial message from asecond UE to initiate the combined ranging session with the plurality ofUEs, wherein the combined ranging session includes the plurality of UEsand the second UE, e.g., as discussed at stages 3A, 3B, 4A, 4B, 5, and 6of FIG. 5. A means for receiving an initial message from a second UE toinitiate the combined ranging session with the plurality of UEs, whereinthe combined ranging session includes the plurality of UEs and thesecond UE may be, e.g., the transceiver 614 and the one or moreprocessors 602 with dedicated hardware or implementing executable codeor software instructions in memory 604 and/or medium 620, such as thepre-PRS message module 622.

In one implementation, the message to the plurality of UEs to combinethe separate ranging sessions and indicating that the first UE willinitiate the combined ranging session further indicates that the firstUE will be a positioning anchor, wherein the combined ranging sessionwith the plurality of UEs comprises a combined positioning session usingthe first UE as the positioning anchor, e.g., as discussed at stages 3Aand 6 of FIG. 5.

In one implementation, the first UE may determine signal strengthcharacteristics of ranging signals in the separate ranging sessionsinitiated by the plurality of UEs, wherein the message to the pluralityof UEs to combine the separate ranging sessions further indicates thesignal strength characteristics of the ranging signals in the separateranging sessions, as discussed at stages 2A and 3A of FIG. 5. A meansfor determining signal strength characteristics of ranging signals inthe separate ranging sessions initiated by the plurality of UEs may be,e.g., the transceiver 614 and the one or more processors 602 withdedicated hardware or implementing executable code or softwareinstructions in memory 604 and/or medium 620, such as the combinesessions module 630.

The combined ranging session includes all UEs that participated in theseparate ranging sessions, including the first UE, the plurality of UEsand plurality of responder UEs, e.g., as discussed at stage 6. In someimplementations, the first UE may determine ranging signals broadcast ina plurality of combined ranging sessions are not received by another UEmore than a predetermined threshold number of times, e.g., as discussedat stage 7A of FIG. 5. The first UE may send a second message to theplurality of UEs to separate the combined ranging sessions andindicating that the plurality of UEs will initiate separate rangingsessions, as discussed at stage 8 of FIG. 5. A means for determiningranging signals broadcast in a plurality of combined ranging sessionsare not received by another UE more than a predetermined thresholdnumber of times and a means for sending a second message to theplurality of UEs to separate the combined ranging sessions andindicating that the plurality of UEs will initiate separate rangingsessions may be, e.g., the transceiver 614 and the one or moreprocessors 602 with dedicated hardware or implementing executable codeor software instructions in memory 604 and/or medium 620, such as theseparate sessions module 632.

In one implementation, the first UE may receive capabilities messagesfrom the plurality of UEs indicating availability of combining rangingsessions, wherein the message sent to the plurality of UEs to combinethe separate ranging sessions is at least partially in response to thecapabilities messages indicating the availability of combining rangingsessions, e.g., as discussed by messages 201 in FIG. 2 and stage 2A ofFIG. 5. A means for receiving capabilities messages from the pluralityof UEs indicating availability of combining ranging sessions, whereinthe message sent to the plurality of UEs to combine the separate rangingsessions is at least partially in response to the capabilities messagesindicating the availability of combining ranging sessions may be, e.g.,the transceiver 614 and the one or more processors 602 with dedicatedhardware or implementing executable code or software instructions inmemory 604 and/or medium 620, such as the combine sessions module 630.

FIG. 8 is a flow chart 800 illustrating a method of ranging between UEsperformed by a first UE, such as UE1 302.

At block 802, the first UE sends an initial message to a second UE toinitiate a first ranging session, such as discussed at stage 1A of FIG.5. A means for sending an initial message to a second UE to initiate afirst ranging session may be, e.g., the transceiver 614 and the one ormore processors 602 with dedicated hardware or implementing executablecode or software instructions in memory 604 and/or medium 620, such asthe pre-PRS message module 622.

At block 804, the first UE receives a message from the second UE tocombine the first ranging session with a second ranging sessioninitiated by a third UE and indicating that the second UE will initiatea combined ranging session, such as discussed at stage 3A of FIG. 5. Thefirst UE, the second UE, and the third UE, for example, may each be oneof a vehicle-based UE, a pedestrian based UE, or a roadside unit. Ameans for receiving a message from the second UE to combine the firstranging session with a second ranging session initiated by a third UEand indicating that the second UE will initiate a combined rangingsession may be, e.g., the transceiver 614 and the one or more processors602 with dedicated hardware or implementing executable code or softwareinstructions in memory 604 and/or medium 620, such as the combinesessions module 630.

At block 806, the first UE performs the combined ranging session withthe second UE, such as discussed at stage 6 of FIG. 5. A means forperforming the combined ranging session with the second UE may be, e.g.,the transceiver 614 and the one or more processors 602 with dedicatedhardware or implementing executable code or software instructions inmemory 604 and/or medium 620, such as the pre-PRS message module 622,PRS module 624, post-PRS message module 626, and ranging/positioningmodule 628.

In one implementation, the second UE may determine that the firstranging session and the second ranging session are concurrent beforesending the message to combine the first ranging session and the secondranging session, e.g., as discussed at stage 2A of FIG. 5. In oneimplementation, the second UE may determine that the first UE and thethird UE have initiated separate ranging sessions more than apredetermined number of times before sending the message to combine thefirst ranging session and the second ranging session, e.g., as discussedat stage 2A of FIG. 5.

In one implementation, the first UE may receive an initial message fromthe second UE to initiate the combined ranging session, e.g., asdiscussed at stage 6 of FIG. 5. A means for receiving an initial messagefrom the second UE to initiate the combined ranging session may be,e.g., the transceiver 614 and the one or more processors 602 withdedicated hardware or implementing executable code or softwareinstructions in memory 604 and/or medium 620, such as the pre-PRSmessage module 622. For example, the first UE may send a responsemessage to the second UE indicating that the second UE will initiate thecombined ranging session, e.g., as discussed at stage 5 of FIG. 5. Ameans for sending a response message to the second UE indicating thatthe second UE will initiate the combined ranging session may be, e.g.,the transceiver 614 and the one or more processors 602 with dedicatedhardware or implementing executable code or software instructions inmemory 604 and/or medium 620, such as the combine sessions module 630.The initial message, for example, may be sent by broadcasting theinitial message to the second UE and a fourth UE to initiate the firstranging session, and the first UE may receive a second message from thefourth UE to combine the first ranging session with the second rangingsession initiated by the third UE and indicating that the fourth UE willinitiate the combined ranging session, e.g., as discussed at stage 3B ofFIG. 5. The first UE may send the response message to the second UEindicating that the second UE will initiate the combined rangingsession, e.g., as discussed at stage 5 of FIG. 5. The first UE mayreceive an initial message from the second UE to initiate the combinedranging session, wherein the combined ranging session includes thesecond UE, the third UE, and the fourth UE, e.g., as discussed at stage6 of FIG. 5. A means for receiving a second message from the fourth UEto combine the first ranging session with the second ranging sessioninitiated by the third UE and indicating that the fourth UE willinitiate the combined ranging session may be, e.g., may be, e.g., thetransceiver 614 and the one or more processors 602 with dedicatedhardware or implementing executable code or software instructions inmemory 604 and/or medium 620, such as the combine sessions module 630. Ameans for receiving an initial message from the second UE to initiatethe combined ranging session, wherein the combined ranging sessionincludes the second UE, the third UE, and the fourth UE may be, e.g.,the transceiver 614 and the one or more processors 602 with dedicatedhardware or implementing executable code or software instructions inmemory 604 and/or medium 620, such as the pre-PRS message module 622. Inone example, the message from the second UE may indicate that the secondUE will be a positioning anchor and the second message from the fourthUE does not indicate that the fourth UE will be a positioning anchor,wherein the response message to the second UE indicating that the secondUE will initiate the combined ranging session is sent in response to thesecond UE indicating that the second UE will be a positioning anchor,wherein the combined ranging session comprises a combined positioningsession using the second UE as the positioning anchor, e.g., asdiscussed at stage 4A of FIG. 5. In another example, the message fromthe second UE may further indicate a first value of a signal strengthcharacteristic for ranging signals in the first ranging session and thesecond ranging sessions measured by the second UE and the second messagefrom the fourth UE indicates a second value of the signal strengthcharacteristic for the ranging signals in the first ranging session andthe second ranging sessions measured by the fourth UE, wherein theresponse message to the second UE indicating that the second UE willinitiate the combined ranging session is sent in response to the firstvalue of the signal strength characteristic being greater than thesecond value of the signal strength characteristic, e.g., as discussedat stage 4A of FIG. 5.

The combined ranging session includes all UEs that participated in thefirst ranging session and the second ranging session, including thefirst UE, the second UE, the third UE, and a plurality of responder UEs,e.g., as discussed at stage 6. In some implementations, the first UE mayreceive a second message from the second UE to separate the combinedranging sessions and indicating that the first UE will initiate theranging sessions in response to the second UE determining that rangingsignals broadcast in a plurality of combined ranging sessions is notreceived by another UE more than a predetermined threshold number oftimes, e.g., as discussed at stage 7A of FIG. 5. A means for receiving asecond message from the second UE to separate the combined rangingsessions and indicating that the first UE will initiate the rangingsessions in response to the second UE determining that ranging signalsbroadcast in a plurality of combined ranging sessions is not received byanother UE more than a predetermined threshold number of times may be,e.g., the transceiver 614 and the one or more processors 602 withdedicated hardware or implementing executable code or softwareinstructions in memory 604 and/or medium 620, such as the separatesessions module 632.

In one implementation, the first UE may send a capability messageindicating availability of combining ranging sessions, e.g., asillustrated by messages 201 in FIG. 2 and discussed at stage 2A in FIG.5. A means for sending a capability message indicating availability ofcombining ranging sessions may be, e.g., the transceiver 614 and the oneor more processors 602 with dedicated hardware or implementingexecutable code or software instructions in memory 604 and/or medium620, such as the combine sessions module 630.

Reference throughout this specification to “one example”, “an example”,“certain examples”, or “exemplary implementation” means that aparticular feature, structure, or characteristic described in connectionwith the feature and/or example may be included in at least one featureand/or example of claimed subject matter. Thus, the appearances of thephrase “in one example”, “an example”, “in certain examples” or “incertain implementations” or other like phrases in various placesthroughout this specification are not necessarily all referring to thesame feature, example, and/or limitation. Furthermore, the particularfeatures, structures, or characteristics may be combined in one or moreexamples and/or features.

Some portions of the detailed description included herein are presentedin terms of algorithms or symbolic representations of operations onbinary digital signals stored within a memory of a specific apparatus orspecial purpose computing device or platform. In the context of thisparticular specification, the term specific apparatus or the likeincludes a general-purpose computer once it is programmed to performparticular operations pursuant to instructions from program software.Algorithmic descriptions or symbolic representations are examples oftechniques used by those of ordinary skill in the signal processing orrelated arts to convey the substance of their work to others skilled inthe art. An algorithm is here, and generally, is considered to be aself-consistent sequence of operations or similar signal processingleading to a desired result. In this context, operations or processinginvolve physical manipulation of physical quantities. Typically,although not necessarily, such quantities may take the form ofelectrical or magnetic signals capable of being stored, transferred,combined, compared, or otherwise manipulated. It has proven convenientat times, principally for reasons of common usage, to refer to suchsignals as bits, data, values, elements, symbols, characters, terms,numbers, numerals, or the like. It should be understood, however, thatall of these or similar terms are to be associated with appropriatephysical quantities and are merely convenient labels. Unlessspecifically stated otherwise, as apparent from the discussion herein,it is appreciated that throughout this specification discussionsutilizing terms such as “processing,” “computing,” “calculating,”“determining” or the like refer to actions or processes of a specificapparatus, such as a special purpose computer, special purpose computingapparatus or a similar special purpose electronic computing device. Inthe context of this specification, therefore, a special purpose computeror a similar special purpose electronic computing device is capable ofmanipulating or transforming signals, typically represented as physicalelectronic or magnetic quantities within memories, registers, or otherinformation storage devices, transmission devices, or display devices ofthe special purpose computer or similar special purpose electroniccomputing device.

In the preceding detailed description, numerous specific details havebeen set forth to provide a thorough understanding of claimed subjectmatter. However, it will be understood by those skilled in the art thatclaimed subject matter may be practiced without these specific details.In other instances, methods and apparatuses that would be known by oneof ordinary skill have not been described in detail so as not to obscureclaimed subject matter.

The terms, “and”, “or”, and “and/or” as used herein may include avariety of meanings that also are expected to depend at least in partupon the context in which such terms are used. Typically, “or” if usedto associate a list, such as A, B or C, is intended to mean A, B, and C,here used in the inclusive sense, as well as A, B or C, here used in theexclusive sense. In addition, the term “one or more” as used herein maybe used to describe any feature, structure, or characteristic in thesingular or may be used to describe a plurality or some othercombination of features, structures, or characteristics. Though, itshould be noted that this is merely an illustrative example and claimedsubject matter is not limited to this example.

While there has been illustrated and described what are presentlyconsidered to be example features, it will be understood by thoseskilled in the art that various other modifications may be made, andequivalents may be substituted, without departing from claimed subjectmatter. Additionally, many modifications may be made to adapt aparticular situation to the teachings of claimed subject matter withoutdeparting from the central concept described herein.

Implementation examples are described in the following numbered clauses:

1. A method of ranging between user equipments (UEs) performed by afirst UE, the method comprising:

receiving initial messages to initiate separate ranging sessions from aplurality of UEs;

sending a message to the plurality of UEs to combine the separateranging sessions and indicating that the first UE will initiate thecombined ranging session; and

performing the combined ranging session with the plurality of UEs.

2. The method of clause 1, further comprising determining that theseparate ranging sessions are concurrent before sending the message tothe plurality of UEs to combine the separate ranging sessions.

3. The method of either of clauses 1 or 2, further comprisingdetermining that the plurality of UEs initiate separate ranging sessionsmore than a predetermined number of times before sending the message tothe plurality of UEs to combine the separate ranging sessions.

4. The method of any of clauses 1-3, further comprising sending aninitial message to the plurality of UEs to initiate the combined rangingsession to the plurality of UEs.

5. The method of clause 4, further comprising receiving responsemessages from the plurality of UEs indicating that each UE in theplurality of UEs accepts that the first UE will initiate the combinedranging session before sending the initial message to initiate thecombined ranging session to the plurality of UEs.

6. The method of any of clauses 1-5, wherein performing the combinedranging session with the plurality of UEs comprises:

receiving an initial message from a second UE to initiate the combinedranging session with the plurality of UEs, wherein the combined rangingsession includes the plurality of UEs and the second UE.

7. The method of any of clauses 1-6, wherein the message to theplurality of UEs to combine the separate ranging sessions and indicatingthat the first UE will initiate the combined ranging session furtherindicates that the first UE will be a positioning anchor, wherein thecombined ranging session with the plurality of UEs comprises a combinedpositioning session using the first UE as the positioning anchor.

8. The method of any of clauses 1-7, further comprising:

determining signal strength characteristics of ranging signals in theseparate ranging sessions initiated by the plurality of UEs;

wherein the message to the plurality of UEs to combine the separateranging sessions further indicates the signal strength characteristicsof the ranging signals in the separate ranging sessions.

9. The method of any of clauses 1-8, wherein the combined rangingsession includes all UEs that participated in the separate rangingsessions, including the first UE, the plurality of UEs and plurality ofresponder UEs.

10. The method of clause 9, the method further comprising:

determining ranging signals broadcast in a plurality of combined rangingsessions is not received by another UE more than a predeterminedthreshold number of times;

sending a second message to the plurality of UEs to separate thecombined ranging sessions and indicating that the plurality of UEs willinitiate separate ranging sessions.

11. The method of clauses 1-10, further comprising receivingcapabilities messages from the plurality of UEs indicating availabilityof combining ranging sessions, wherein the message sent to the pluralityof UEs to combine the separate ranging sessions is at least partially inresponse to the capabilities messages indicating the availability ofcombining ranging sessions.

12. The method of any of clauses 1-11, wherein the first UE and theplurality of UEs are each one of a vehicle based UE, a pedestrian basedUE, or a road side unit.

13. A first user equipment (UE) configured for ranging between UEs, thefirst UE comprising:

a wireless transceiver configured to wirelessly communicate withentities in a wireless network;

at least one memory; and

at least one processor coupled to the wireless transceiver and the atleast one memory, wherein the at least one processor is configured to:

receive, via the wireless transceiver, initial messages to initiateseparate ranging sessions from a plurality of UEs;

send, via the wireless transceiver, a message to the plurality of UEs tocombine the separate ranging sessions and indicating that the first UEwill initiate the combined ranging session; and

perform the combined ranging session with the plurality of UEs.

14. The first UE of clause 13, wherein the at least one processor isfurther configured to determine that the separate ranging sessions areconcurrent before sending the message to the plurality of UEs to combinethe separate ranging sessions.

15. The first UE of either of clauses 13 or 14, wherein the at least oneprocessor is further configured to determine that the plurality of UEsinitiate separate ranging sessions more than a predetermined number oftimes before sending the message to the plurality of UEs to combine theseparate ranging sessions.

16. The first UE of any of clauses 13-15, wherein the at least oneprocessor is further configured to send an initial message to theplurality of UEs to initiate the combined ranging session to theplurality of UEs.

17. The first UE of clause 16, wherein the at least one processor isfurther configured to receive response messages from the plurality ofUEs indicating that each UE in the plurality of UEs accepts that thefirst UE will initiate the combined ranging session before sending theinitial message to initiate the combined ranging session to theplurality of UEs.

18. The first UE of any of clauses 13-17, wherein the at least oneprocessor is configured to perform the combined ranging session with theplurality of UEs by being configured to:

receive, via the wireless transceiver, an initial message from a secondUE to initiate the combined ranging session with the plurality of UEs,wherein the combined ranging session includes the plurality of UEs andthe second UE.

19. The first UE of any of clauses 13-18, wherein the message to theplurality of UEs to combine the separate ranging sessions and indicatingthat the first UE will initiate the combined ranging session furtherindicates that the first UE will be a positioning anchor, wherein thecombined ranging session with the plurality of UEs comprises a combinedpositioning session using the first UE as the positioning anchor.

20. The first UE of any of clauses 13-19, wherein the at least oneprocessor is further configured to:

determine signal strength characteristics of ranging signals in theseparate ranging sessions initiated by the plurality of UEs;

wherein the message to the plurality of UEs to combine the separateranging sessions further indicates the signal strength characteristicsof the ranging signals in the separate ranging sessions.

21. The first UE of any of clauses 13-20, wherein the combined rangingsession includes all UEs that participated in the separate rangingsessions, including the first UE, the plurality of UEs and plurality ofresponder UEs.

22. The first UE of clause 21, wherein the at least one processor isfurther configured to:

determine ranging signals broadcast in a plurality of combined rangingsessions is not received by another UE more than a predeterminedthreshold number of times;

send, via the wireless transceiver, a second message to the plurality ofUEs to separate the combined ranging sessions and indicating that theplurality of UEs will initiate separate ranging sessions.

23. The first UE of any of clauses 13-22, wherein the at least oneprocessor is further configured to receive, via the wirelesstransceiver, capabilities messages from the plurality of UEs indicatingavailability of combining ranging sessions, wherein the message sent tothe plurality of UEs to combine the separate ranging sessions is atleast partially in response to the capabilities messages indicating theavailability of combining ranging sessions.

24. The first UE of any of clauses 13-23, wherein the first UE and theplurality of UEs are each one of a vehicle based UE, a pedestrian basedUE, or a road side unit.

25. A first user equipment (UE) configured for ranging between UEs, thefirst UE comprising:

means for receiving initial messages to initiate separate rangingsessions from a plurality of UEs;

means for sending a message to the plurality of UEs to combine theseparate ranging sessions and indicating that the first UE will initiatethe combined ranging session; and

means for performing the combined ranging session with the plurality ofUEs.

26. The first UE of clause 25, further comprising means for determiningthat the separate ranging sessions are concurrent before sending themessage to the plurality of UEs to combine the separate rangingsessions.

27. The first UE of either of clauses 25 or 26, further comprising meansfor determining that the plurality of UEs initiate separate rangingsessions more than a predetermined number of times before sending themessage to the plurality of UEs to combine the separate rangingsessions.

28. The first UE of any of clauses 25-27, further comprising means forsending an initial message to the plurality of UEs to initiate thecombined ranging session to the plurality of UEs.

29. The first UE of clause 28, further comprising means for receivingresponse messages from the plurality of UEs indicating that each UE inthe plurality of UEs accepts that the first UE will initiate thecombined ranging session before sending the initial message to initiatethe combined ranging session to the plurality of UEs.

30. The first UE of any of clauses 25-29, wherein means for performingthe combined ranging session with the plurality of UEs comprises:

means for receiving an initial message from a second UE to initiate thecombined ranging session with the plurality of UEs, wherein the combinedranging session includes the plurality of UEs and the second UE.

31. The first UE of any of clauses 25-30, wherein the message to theplurality of UEs to combine the separate ranging sessions and indicatingthat the first UE will initiate the combined ranging session furtherindicates that the first UE will be a positioning anchor, wherein thecombined ranging session with the plurality of UEs comprises a combinedpositioning session using the first UE as the positioning anchor.

32. The first UE of any of clauses 25-31, further comprising:

means for determining signal strength characteristics of ranging signalsin the separate ranging sessions initiated by the plurality of UEs;

wherein the message to the plurality of UEs to combine the separateranging sessions further indicates the signal strength characteristicsof the ranging signals in the separate ranging sessions.

33. The first UE of any of clauses 25-32, wherein the combined rangingsession includes all UEs that participated in the separate rangingsessions, including the first UE, the plurality of UEs and plurality ofresponder UEs.

34. The first UE of clause 33, further comprising:

means for determining ranging signals broadcast in a plurality ofcombined ranging sessions is not received by another UE more than apredetermined threshold number of times;

means for sending a second message to the plurality of UEs to separatethe combined ranging sessions and indicating that the plurality of UEswill initiate separate ranging sessions.

35. The first UE of clauses 25-34, further comprising means forreceiving capabilities messages from the plurality of UEs indicatingavailability of combining ranging sessions, wherein the message sent tothe plurality of UEs to combine the separate ranging sessions is atleast partially in response to the capabilities messages indicating theavailability of combining ranging sessions.

36. The first UE of any of clauses 25-35, wherein the first UE and theplurality of UEs are each one of a vehicle based UE, a pedestrian basedUE, or a road side unit.

37. A non-transitory storage medium including program code storedthereon, the program code is operable to configure at least oneprocessor in a first user equipment (UE) for ranging between UEs, theprogram code comprising instructions to:

receive initial messages to initiate separate ranging sessions from aplurality of UEs;

send a message to the plurality of UEs to combine the separate rangingsessions and indicating that the first UE will initiate the combinedranging session; and

perform the combined ranging session with the plurality of UEs.

38. The non-transitory storage medium including program code of clause37, further comprising program code to determine that the separateranging sessions are concurrent before sending the message to theplurality of UEs to combine the separate ranging sessions.

39. The non-transitory storage medium including program code of eitherof clauses 37 or 38, further comprising program code to determine thatthe plurality of UEs initiate separate ranging sessions more than apredetermined number of times before sending the message to theplurality of UEs to combine the separate ranging sessions.

40. The non-transitory storage medium including program code of any ofclauses 37-39, further comprising program code to send an initialmessage to the plurality of UEs to initiate the combined ranging sessionto the plurality of UEs.

41. The non-transitory storage medium including program code of clause40, further comprising program code to receive response messages fromthe plurality of UEs indicating that each UE in the plurality of UEsaccepts that the first UE will initiate the combined ranging sessionbefore sending the initial message to initiate the combined rangingsession to the plurality of UEs.

42. The non-transitory storage medium including program code of any ofclauses 37-41, wherein the program code to performing the combinedranging session with the plurality of UEs comprises program code to:

receive an initial message from a second UE to initiate the combinedranging session with the plurality of UEs, wherein the combined rangingsession includes the plurality of UEs and the second UE.

43. The non-transitory storage medium including program code of any ofclauses 37-42, wherein the message to the plurality of UEs to combinethe separate ranging sessions and indicating that the first UE willinitiate the combined ranging session further indicates that the firstUE will be a positioning anchor, wherein the combined ranging sessionwith the plurality of UEs comprises a combined positioning session usingthe first UE as the positioning anchor.

44. The non-transitory storage medium including program code of any ofclauses 37-43, further comprising program code to:

determine signal strength characteristics of ranging signals in theseparate ranging sessions initiated by the plurality of UEs;

wherein the message to the plurality of UEs to combine the separateranging sessions further indicates the signal strength characteristicsof the ranging signals in the separate ranging sessions.

45. The non-transitory storage medium including program code of any ofclauses 37-44, wherein the combined ranging session includes all UEsthat participated in the separate ranging sessions, including the firstUE, the plurality of UEs and plurality of responder UEs.

46. The non-transitory storage medium including program code of clause45, further comprising program code to:

determine ranging signals broadcast in a plurality of combined rangingsessions is not received by another UE more than a predeterminedthreshold number of times;

send a second message to the plurality of UEs to separate the combinedranging sessions and indicating that the plurality of UEs will initiateseparate ranging sessions.

47. The non-transitory storage medium including program code of any ofclauses 37-46, further comprising program code to receive capabilitiesmessages from the plurality of UEs indicating availability of combiningranging sessions, wherein the message sent to the plurality of UEs tocombine the separate ranging sessions is at least partially in responseto the capabilities messages indicating the availability of combiningranging sessions.

48. The non-transitory storage medium including program code of any ofclauses 37-47, wherein the first UE and the plurality of UEs are eachone of a vehicle based UE, a pedestrian based UE, or a road side unit.

49. A method of ranging between user equipments (UEs) performed by afirst UE, the method comprising:

sending an initial message to a second UE to initiate a first rangingsession;

receiving a message from the second UE to combine the first rangingsession with a second ranging session initiated by a third UE andindicating that the second UE will initiate a combined ranging session;and

performing the combined ranging session with the second UE.

50. The method of clause 49, wherein the second UE determines that thefirst ranging session and the second ranging session are concurrentbefore sending the message to combine the first ranging session and thesecond ranging session.

51. The method of either of clauses 49 or 50, wherein the second UEdetermines that the first UE and the third UE have initiated separateranging sessions more than a predetermined number of times beforesending the message to combine the first ranging session and the secondranging session.

52. The method of any of clauses 49-51, further comprising receiving aninitial message from the second UE to initiate the combined rangingsession.

53. The method of clause 52, further comprising sending a responsemessage to the second UE indicating that the second UE will initiate thecombined ranging session.

54. The method of clause 53, wherein sending the initial messagecomprises broadcasting the initial message to the second UE and a fourthUE to initiate the first ranging session, the method further comprising:

receiving a second message from the fourth UE to combine the firstranging session with the second ranging session initiated by the thirdUE and indicating that the fourth UE will initiate the combined rangingsession;

sending the response message to the second UE indicating that the secondUE will initiate the combined ranging session;

receiving an initial message from the second UE to initiate the combinedranging session;

wherein the combined ranging session includes the second UE, the thirdUE, and the fourth UE.

55. The method of clause 54, wherein the message from the second UEindicates that the second UE will be a positioning anchor and the secondmessage from the fourth UE does not indicates that the fourth UE will bea positioning anchor, and wherein sending the response message to thesecond UE indicating that the second UE will initiate the combinedranging session is in response to the second UE indicating that thesecond UE will be a positioning anchor, wherein the combined rangingsession comprises a combined positioning session using the second UE asthe positioning anchor.

56. The method of clause 54, wherein the message from the second UEfurther indicates a first value of a signal strength characteristic forranging signals in the first ranging session and the second rangingsessions measured by the second UE and the second message from thefourth UE indicates a second value of the signal strength characteristicfor the ranging signals in the first ranging session and the secondranging sessions measured by the fourth UE, and wherein sending theresponse message to the second UE indicating that the second UE willinitiate the combined ranging session is in response to the first valueof the signal strength characteristic being greater than the secondvalue of the signal strength characteristic.

57. The method of any of clauses 49-56, wherein the combined rangingsession includes all UEs that participated in the first ranging sessionand the second ranging session, including the first UE, the second UE,the third UE, and a plurality of responder UEs.

58. The method of clause 57, the method further comprising:

receiving a second message from the second UE to separate the combinedranging sessions and indicating that the first UE will initiate theranging sessions in response to the second UE determining that rangingsignals broadcast in a plurality of combined ranging sessions is notreceived by another UE more than a predetermined threshold number oftimes.

59. The method of clauses 49-58, further comprising sending a capabilitymessage indicating availability of combining ranging sessions.

60. The method of any of clauses 49-59, wherein the first UE, the secondUE, and the third UE are each one of a vehicle based UE, a pedestrianbased UE, or a road side unit.

61. A first user equipment (UE) configured for ranging between UEs, thefirst UE comprising:

a wireless transceiver configured to wirelessly communicate withentities in a wireless network;

at least one memory; and

at least one processor coupled to the wireless transceiver and the atleast one memory, wherein the at least one processor is configured to:

send, via the wireless transceiver, an initial message to a second UE toinitiate a first ranging session;

receive, via the wireless transceiver, a message from the second UE tocombine the first ranging session with a second ranging sessioninitiated by a third UE and indicating that the second UE will initiatea combined ranging session; and

perform the combined ranging session with the second UE.

62. The first UE of clause 61, wherein the second UE determines that thefirst ranging session and the second ranging session are concurrentbefore sending the message to combine the first ranging session and thesecond ranging session.

63. The first UE of either of clauses 61 or 62, wherein the second UEdetermines that the first UE and the third UE have initiated separateranging sessions more than a predetermined number of times beforesending the message to combine the first ranging session and the secondranging session.

64. The first UE of any of clauses 61-63, wherein the at least oneprocessor is further configured to receive an initial message from thesecond UE to initiate the combined ranging session.

65. The first UE of clause 64, wherein the at least one processor isfurther configured to send a response message to the second UEindicating that the second UE will initiate the combined rangingsession.

66. The first UE of clause 65, wherein the at least one processor isconfigured to send the initial message by being configured to broadcastthe initial message to the second UE and a fourth UE to initiate thefirst ranging session, the at least one processor is further configuredto:

receive, via the wireless transceiver, a second message from the fourthUE to combine the first ranging session with the second ranging sessioninitiated by the third UE and indicating that the fourth UE willinitiate the combined ranging session;

send, via the wireless transceiver, the response message to the secondUE indicating that the second UE will initiate the combined rangingsession;

receive, via the wireless transceiver, an initial message from thesecond UE to initiate the combined ranging session;

wherein the combined ranging session includes the second UE, the thirdUE, and the fourth UE.

67. The first UE of clause 66, wherein the message from the second UEindicates that the second UE will be a positioning anchor and the secondmessage from the fourth UE does not indicates that the fourth UE will bea positioning anchor, and wherein the at least one processor isconfigured to send the response message to the second UE indicating thatthe second UE will initiate the combined ranging session is in responseto the second UE indicating that the second UE will be a positioninganchor, wherein the combined ranging session comprises a combinedpositioning session using the second UE as the positioning anchor.

68. The first UE of clause 66, wherein the message from the second UEfurther indicates a first value of a signal strength characteristic forranging signals in the first ranging session and the second rangingsessions measured by the second UE and the second message from thefourth UE indicates a second value of the signal strength characteristicfor the ranging signals in the first ranging session and the secondranging sessions measured by the fourth UE, and wherein the at least oneprocessor is configured to send the response message to the second UEindicating that the second UE will initiate the combined ranging sessionis in response to the first value of the signal strength characteristicbeing greater than the second value of the signal strengthcharacteristic.

69. The first UE of any of clauses 61-68, wherein the combined rangingsession includes all UEs that participated in the first ranging sessionand the second ranging session, including the first UE, the second UE,the third UE, and a plurality of responder UEs.

70. The first UE of clause 69, wherein the at least one processor isfurther configured to:

receive, via the wireless transceiver, a second message from the secondUE to separate the combined ranging sessions and indicating that thefirst UE will initiate the ranging sessions in response to the second UEdetermining that ranging signals broadcast in a plurality of combinedranging sessions is not received by another UE more than a predeterminedthreshold number of times.

71. The first UE of any of clauses 61-70, wherein the at least oneprocessor is further configured to send, via the wireless transceiver, acapability message indicating availability of combining rangingsessions.

72. The first UE of any of clauses 61-71, wherein the first UE, thesecond UE, and the third UE are each one of a vehicle based UE, apedestrian based UE, or a road side unit.

73. A first user equipment (UE) configured for ranging between UEs, thefirst UE comprising:

means for sending an initial message to a second UE to initiate a firstranging session;

means for receiving a message from the second UE to combine the firstranging session with a second ranging session initiated by a third UEand indicating that the second UE will initiate a combined rangingsession; and

means for performing the combined ranging session with the second UE.

74. The first UE of clause 73, wherein the second UE determines that thefirst ranging session and the second ranging session are concurrentbefore sending the message to combine the first ranging session and thesecond ranging session.

75. The first UE of either of clauses 73 or 74, wherein the second UEdetermines that the first UE and the third UE have initiated separateranging sessions more than a predetermined number of times beforesending the message to combine the first ranging session and the secondranging session.

76. The first UE of any of clauses 73-75, further comprising means forreceiving an initial message from the second UE to initiate the combinedranging session.

77. The first UE of clause 76, further comprising means for sending aresponse message to the second UE indicating that the second UE willinitiate the combined ranging session.

78. The first UE of clause 77, wherein the means for sending the initialmessage comprises broadcasting the initial message to the second UE anda fourth UE to initiate the first ranging session comprises:

means for receiving a second message from the fourth UE to combine thefirst ranging session with the second ranging session initiated by thethird UE and indicating that the fourth UE will initiate the combinedranging session;

means for sending the response message to the second UE indicating thatthe second UE will initiate the combined ranging session;

means for receiving an initial message from the second UE to initiatethe combined ranging session;

wherein the combined ranging session includes the second UE, the thirdUE, and the fourth UE.

79. The first UE of clause 78, wherein the message from the second UEindicates that the second UE will be a positioning anchor and the secondmessage from the fourth UE does not indicates that the fourth UE will bea positioning anchor, and wherein the means for sending the responsemessage to the second UE indicating that the second UE will initiate thecombined ranging session responds to the second UE indicating that thesecond UE will be a positioning anchor, wherein the combined rangingsession comprises a combined positioning session using the second UE asthe positioning anchor.

80. The first UE of clause 78, wherein the message from the second UEfurther indicates a first value of a signal strength characteristic forranging signals in the first ranging session and the second rangingsessions measured by the second UE and the second message from thefourth UE indicates a second value of the signal strength characteristicfor the ranging signals in the first ranging session and the secondranging sessions measured by the fourth UE, and wherein the means forsending the response message to the second UE indicating that the secondUE will initiate the combined ranging session responds to the firstvalue of the signal strength characteristic being greater than thesecond value of the signal strength characteristic.

81. The first UE of any of clauses 73-80, wherein the combined rangingsession includes all UEs that participated in the first ranging sessionand the second ranging session, including the first UE, the second UE,the third UE, and a plurality of responder UEs.

82. The first UE of clause 81, further comprising:

means for receiving a second message from the second UE to separate thecombined ranging sessions and indicating that the first UE will initiatethe ranging sessions in response to the second UE determining thatranging signals broadcast in a plurality of combined ranging sessions isnot received by another UE more than a predetermined threshold number oftimes.

83. The first UE of any of clauses 73-82, further comprising sending acapability message indicating availability of combining rangingsessions.

84. The first UE of any of clauses 73-83, wherein the first UE, thesecond UE, and the third UE are each one of a vehicle based UE, apedestrian based UE, or a road side unit.

85. A non-transitory storage medium including program code storedthereon, the program code is operable to configure at least oneprocessor in a first user equipment (UE) for ranging between UEs, theprogram code comprising instructions to:

send an initial message to a second UE to initiate a first rangingsession;

receive a message from the second UE to combine the first rangingsession with a second ranging session initiated by a third UE andindicating that the second UE will initiate a combined ranging session;and

perform the combined ranging session with the second UE.

86. The non-transitory storage medium including program code of clause85, wherein the second UE determines that the first ranging session andthe second ranging session are concurrent before sending the message tocombine the first ranging session and the second ranging session.

87. The non-transitory storage medium including program code of eitherof clauses 85 or 86, wherein the second UE determines that the first UEand the third UE have initiated separate ranging sessions more than apredetermined number of times before sending the message to combine thefirst ranging session and the second ranging session.

88. The non-transitory storage medium including program code of any ofclauses 85-87, further comprising program code to receive an initialmessage from the second UE to initiate the combined ranging session.

89. The non-transitory storage medium including program code of clause88, further comprising program code to send a response message to thesecond UE indicating that the second UE will initiate the combinedranging session.

90. The non-transitory storage medium including program code of clause89, wherein the program code to send the initial message comprisesprogram code to broadcast the initial message to the second UE and afourth UE to initiate the first ranging session, further comprisingprogram code to:

receive a second message from the fourth UE to combine the first rangingsession with the second ranging session initiated by the third UE andindicating that the fourth UE will initiate the combined rangingsession;

send the response message to the second UE indicating that the second UEwill initiate the combined ranging session;

receive an initial message from the second UE to initiate the combinedranging session;

wherein the combined ranging session includes the second UE, the thirdUE, and the fourth UE.

91. The non-transitory storage medium including program code of clause90, wherein the message from the second UE indicates that the second UEwill be a positioning anchor and the second message from the fourth UEdoes not indicates that the fourth UE will be a positioning anchor, andwherein the program code to send the response message to the second UEindicating that the second UE will initiate the combined ranging sessionresponds to the second UE indicating that the second UE will be apositioning anchor, wherein the combined ranging session comprises acombined positioning session using the second UE as the positioninganchor.

92. The non-transitory storage medium including program code of clause90, wherein the message from the second UE further indicates a firstvalue of a signal strength characteristic for ranging signals in thefirst ranging session and the second ranging sessions measured by thesecond UE and the second message from the fourth UE indicates a secondvalue of the signal strength characteristic for the ranging signals inthe first ranging session and the second ranging sessions measured bythe fourth UE, and wherein the program code to send the response messageto the second UE indicating that the second UE will initiate thecombined ranging session responds to the first value of the signalstrength characteristic being greater than the second value of thesignal strength characteristic.

93. The non-transitory storage medium including program code of any ofclauses 85-92, wherein the combined ranging session includes all UEsthat participated in the first ranging session and the second rangingsession, including the first UE, the second UE, the third UE, and aplurality of responder UEs.

94. The non-transitory storage medium including program code of clause93, further comprising program code to:

receive a second message from the second UE to separate the combinedranging sessions and indicating that the first UE will initiate theranging sessions in response to the second UE determining that rangingsignals broadcast in a plurality of combined ranging sessions is notreceived by another UE more than a predetermined threshold number oftimes.

95. The non-transitory storage medium including program code of any ofclauses 85-94, further comprising program code to send a capabilitymessage indicating availability of combining ranging sessions.

96. The non-transitory storage medium including program code of any ofclauses 85-95, wherein the first UE, the second UE, and the third UE areeach one of a vehicle based UE, a pedestrian based UE, or a road sideunit.

Therefore, it is intended that claimed subject matter not be limited tothe particular examples disclosed, but that such claimed subject mattermay also include all aspects falling within the scope of appendedclaims, and equivalents thereof.

What is claimed is:
 1. A method of ranging between user equipments (UEs)performed by a first UE, the method comprising: receiving initialmessages to initiate separate ranging sessions from a plurality of UEs;sending a message to the plurality of UEs to combine the separateranging sessions and indicating that the first UE will initiate thecombined ranging session; and performing the combined ranging sessionwith the plurality of UEs.
 2. The method of claim 1, further comprisingdetermining that the separate ranging sessions are concurrent beforesending the message to the plurality of UEs to combine the separateranging sessions.
 3. The method of claim 1, further comprisingdetermining that the plurality of UEs initiate separate ranging sessionsmore than a predetermined number of times before sending the message tothe plurality of UEs to combine the separate ranging sessions.
 4. Themethod of claim 1, further comprising sending an initial message to theplurality of UEs to initiate the combined ranging session to theplurality of UEs.
 5. The method of claim 4, further comprising receivingresponse messages from the plurality of UEs indicating that each UE inthe plurality of UEs accepts that the first UE will initiate thecombined ranging session before sending the initial message to initiatethe combined ranging session to the plurality of UEs.
 6. The method ofclaim 1, wherein performing the combined ranging session with theplurality of UEs comprises: receiving an initial message from a secondUE to initiate the combined ranging session with the plurality of UEs,wherein the combined ranging session includes the plurality of UEs andthe second UE.
 7. The method of claim 1, wherein the message to theplurality of UEs to combine the separate ranging sessions and indicatingthat the first UE will initiate the combined ranging session furtherindicates that the first UE will be a positioning anchor, wherein thecombined ranging session with the plurality of UEs comprises a combinedpositioning session using the first UE as the positioning anchor.
 8. Themethod of claim 1, further comprising: determining signal strengthcharacteristics of ranging signals in the separate ranging sessionsinitiated by the plurality of UEs; wherein the message to the pluralityof UEs to combine the separate ranging sessions further indicates thesignal strength characteristics of the ranging signals in the separateranging sessions.
 9. The method of claim 1, wherein the combined rangingsession includes all UEs that participated in the separate rangingsessions, including the first UE, the plurality of UEs and plurality ofresponder UEs.
 10. The method of claim 9, the method further comprising:determining ranging signals broadcast in a plurality of combined rangingsessions is not received by another UE more than a predeterminedthreshold number of times; sending a second message to the plurality ofUEs to separate the combined ranging sessions and indicating that theplurality of UEs will initiate separate ranging sessions.
 11. The methodof claim 1, further comprising receiving capabilities messages from theplurality of UEs indicating availability of combining ranging sessions,wherein the message sent to the plurality of UEs to combine the separateranging sessions is at least partially in response to the capabilitiesmessages indicating the availability of combining ranging sessions. 12.The method of claim 1, wherein the first UE and the plurality of UEs areeach one of a vehicle based UE, a pedestrian based UE, or a roadsideunit.
 13. A first user equipment (UE) configured for ranging betweenUEs, the first UE comprising: a wireless transceiver configured towirelessly communicate with entities in a wireless network; at least onememory; and at least one processor coupled to the wireless transceiverand the at least one memory, wherein the at least one processor isconfigured to: receive, via the wireless transceiver, initial messagesto initiate separate ranging sessions from a plurality of UEs; send, viathe wireless transceiver, a message to the plurality of UEs to combinethe separate ranging sessions and indicating that the first UE willinitiate the combined ranging session; and perform the combined rangingsession with the plurality of UEs.
 14. The first UE of claim 13, whereinthe at least one processor is further configured to determine that theseparate ranging sessions are concurrent before sending the message tothe plurality of UEs to combine the separate ranging sessions.
 15. Thefirst UE of claim 13, wherein the at least one processor is furtherconfigured to determine that the plurality of UEs initiate separateranging sessions more than a predetermined number of times beforesending the message to the plurality of UEs to combine the separateranging sessions.
 16. The first UE of claim 13, wherein the at least oneprocessor is further configured to send an initial message to theplurality of UEs to initiate the combined ranging session to theplurality of UEs.
 17. The first UE of claim 16, wherein the at least oneprocessor is further configured to receive response messages from theplurality of UEs indicating that each UE in the plurality of UEs acceptsthat the first UE will initiate the combined ranging session beforesending the initial message to initiate the combined ranging session tothe plurality of UEs.
 18. The first UE of claim 13, wherein the at leastone processor is configured to perform the combined ranging session withthe plurality of UEs by being configured to: receive, via the wirelesstransceiver, an initial message from a second UE to initiate thecombined ranging session with the plurality of UEs, wherein the combinedranging session includes the plurality of UEs and the second UE.
 19. Thefirst UE of claim 13, wherein the message to the plurality of UEs tocombine the separate ranging sessions and indicating that the first UEwill initiate the combined ranging session further indicates that thefirst UE will be a positioning anchor, wherein the combined rangingsession with the plurality of UEs comprises a combined positioningsession using the first UE as the positioning anchor.
 20. The first UEof claim 13, wherein the at least one processor is further configuredto: determine signal strength characteristics of ranging signals in theseparate ranging sessions initiated by the plurality of UEs; wherein themessage to the plurality of UEs to combine the separate ranging sessionsfurther indicates the signal strength characteristics of the rangingsignals in the separate ranging sessions.
 21. The first UE of claim 13,wherein the combined ranging session includes all UEs that participatedin the separate ranging sessions, including the first UE, the pluralityof UEs and plurality of responder UEs.
 22. The first UE of claim 21,wherein the at least one processor is further configured to: determineranging signals broadcast in a plurality of combined ranging sessions isnot received by another UE more than a predetermined threshold number oftimes; send, via the wireless transceiver, a second message to theplurality of UEs to separate the combined ranging sessions andindicating that the plurality of UEs will initiate separate rangingsessions.
 23. The first UE of claim 13, wherein the at least oneprocessor is further configured to receive, via the wirelesstransceiver, capabilities messages from the plurality of UEs indicatingavailability of combining ranging sessions, wherein the message sent tothe plurality of UEs to combine the separate ranging sessions is atleast partially in response to the capabilities messages indicating theavailability of combining ranging sessions.
 24. The first UE of claim13, wherein the first UE and the plurality of UEs are each one of avehicle based UE, a pedestrian based UE, or a roadside unit.
 25. A firstuser equipment (UE) configured for ranging between UEs, the first UEcomprising: means for receiving initial messages to initiate separateranging sessions from a plurality of UEs; means for sending a message tothe plurality of UEs to combine the separate ranging sessions andindicating that the first UE will initiate the combined ranging session;and means for performing the combined ranging session with the pluralityof UEs.
 26. The first UE of claim 25, further comprising means fordetermining that the separate ranging sessions are concurrent beforesending the message to the plurality of UEs to combine the separateranging sessions.
 27. The first UE of claim 25, further comprising meansfor determining that the plurality of UEs initiate separate rangingsessions more than a predetermined number of times before sending themessage to the plurality of UEs to combine the separate rangingsessions.
 28. The first UE of claim 25, further comprising means forsending an initial message to the plurality of UEs to initiate thecombined ranging session to the plurality of UEs.
 29. A method ofranging between user equipments (UEs) performed by a first UE, themethod comprising: sending an initial message to a second UE to initiatea first ranging session; receiving a message from the second UE tocombine the first ranging session with a second ranging sessioninitiated by a third UE and indicating that the second UE will initiatea combined ranging session; and performing the combined ranging sessionwith the second UE.
 30. The method of claim 29, wherein the second UEdetermines that the first ranging session and the second ranging sessionare concurrent before sending the message to combine the first rangingsession and the second ranging session.
 31. The method of claim 29,wherein the second UE determines that the first UE and the third UE haveinitiated separate ranging sessions more than a predetermined number oftimes before sending the message to combine the first ranging sessionand the second ranging session.
 32. The method of claim 29, furthercomprising receiving an initial message from the second UE to initiatethe combined ranging session.
 33. The method of claim 32, furthercomprising sending a response message to the second UE indicating thatthe second UE will initiate the combined ranging session.
 34. The methodof claim 33, wherein sending the initial message comprises broadcastingthe initial message to the second UE and a fourth UE to initiate thefirst ranging session, the method further comprising: receiving a secondmessage from the fourth UE to combine the first ranging session with thesecond ranging session initiated by the third UE and indicating that thefourth UE will initiate the combined ranging session; sending theresponse message to the second UE indicating that the second UE willinitiate the combined ranging session; receiving an initial message fromthe second UE to initiate the combined ranging session; wherein thecombined ranging session includes the second UE, the third UE, and thefourth UE.
 35. The method of claim 34, wherein the message from thesecond UE indicates that the second UE will be a positioning anchor andthe second message from the fourth UE does not indicates that the fourthUE will be a positioning anchor, and wherein sending the responsemessage to the second UE indicating that the second UE will initiate thecombined ranging session is in response to the second UE indicating thatthe second UE will be a positioning anchor, wherein the combined rangingsession comprises a combined positioning session using the second UE asthe positioning anchor.
 36. The method of claim 34, wherein the messagefrom the second UE further indicates a first value of a signal strengthcharacteristic for ranging signals in the first ranging session and thesecond ranging sessions measured by the second UE and the second messagefrom the fourth UE indicates a second value of the signal strengthcharacteristic for the ranging signals in the first ranging session andthe second ranging sessions measured by the fourth UE, and whereinsending the response message to the second UE indicating that the secondUE will initiate the combined ranging session is in response to thefirst value of the signal strength characteristic being greater than thesecond value of the signal strength characteristic.
 37. The method ofclaim 29, wherein the combined ranging session includes all UEs thatparticipated in the first ranging session and the second rangingsession, including the first UE, the second UE, the third UE, and aplurality of responder UEs.
 38. The method of claim 37, the methodfurther comprising: receiving a second message from the second UE toseparate the combined ranging sessions and indicating that the first UEwill initiate the ranging sessions in response to the second UEdetermining that ranging signals broadcast in a plurality of combinedranging sessions is not received by another UE more than a predeterminedthreshold number of times.
 39. The method of claim 29, furthercomprising sending a capability message indicating availability ofcombining ranging sessions.
 40. The method of claim 29, wherein thefirst UE, the second UE, and the third UE are each one of a vehiclebased UE, a pedestrian based UE, or a roadside unit.
 41. A first userequipment (UE) configured for ranging between UEs, the first UEcomprising: a wireless transceiver configured to wirelessly communicatewith entities in a wireless network; at least one memory; and at leastone processor coupled to the wireless transceiver and the at least onememory, wherein the at least one processor is configured to: send, viathe wireless transceiver, an initial message to a second UE to initiatea first ranging session; receive, via the wireless transceiver, amessage from the second UE to combine the first ranging session with asecond ranging session initiated by a third UE and indicating that thesecond UE will initiate a combined ranging session; and perform thecombined ranging session with the second UE.
 42. The first UE of claim41, wherein the second UE determines that the first ranging session andthe second ranging session are concurrent before sending the message tocombine the first ranging session and the second ranging session. 43.The first UE of claim 41, wherein the second UE determines that thefirst UE and the third UE have initiated separate ranging sessions morethan a predetermined number of times before sending the message tocombine the first ranging session and the second ranging session. 44.The first UE of claim 41, wherein the at least one processor is furtherconfigured to receive an initial message from the second UE to initiatethe combined ranging session.
 45. The first UE of claim 44, wherein theat least one processor is further configured to send a response messageto the second UE indicating that the second UE will initiate thecombined ranging session.
 46. The first UE of claim 45, wherein the atleast one processor is configured to send the initial message by beingconfigured to broadcast the initial message to the second UE and afourth UE to initiate the first ranging session, the at least oneprocessor is further configured to: receive, via the wirelesstransceiver, a second message from the fourth UE to combine the firstranging session with the second ranging session initiated by the thirdUE and indicating that the fourth UE will initiate the combined rangingsession; send, via the wireless transceiver, the response message to thesecond UE indicating that the second UE will initiate the combinedranging session; receive, via the wireless transceiver, an initialmessage from the second UE to initiate the combined ranging session;wherein the combined ranging session includes the second UE, the thirdUE, and the fourth UE.
 47. The first UE of claim 46, wherein the messagefrom the second UE indicates that the second UE will be a positioninganchor and the second message from the fourth UE does not indicates thatthe fourth UE will be a positioning anchor, and wherein the at least oneprocessor is configured to send the response message to the second UEindicating that the second UE will initiate the combined ranging sessionis in response to the second UE indicating that the second UE will be apositioning anchor, wherein the combined ranging session comprises acombined positioning session using the second UE as the positioninganchor.
 48. The first UE of claim 46, wherein the message from thesecond UE further indicates a first value of a signal strengthcharacteristic for ranging signals in the first ranging session and thesecond ranging sessions measured by the second UE and the second messagefrom the fourth UE indicates a second value of the signal strengthcharacteristic for the ranging signals in the first ranging session andthe second ranging sessions measured by the fourth UE, and wherein theat least one processor is configured to send the response message to thesecond UE indicating that the second UE will initiate the combinedranging session is in response to the first value of the signal strengthcharacteristic being greater than the second value of the signalstrength characteristic.
 49. The first UE of claim 41, wherein thecombined ranging session includes all UEs that participated in the firstranging session and the second ranging session, including the first UE,the second UE, the third UE, and a plurality of responder UEs.
 50. Thefirst UE of claim 49, wherein the at least one processor is furtherconfigured to: receive, via the wireless transceiver, a second messagefrom the second UE to separate the combined ranging sessions andindicating that the first UE will initiate the ranging sessions inresponse to the second UE determining that ranging signals broadcast ina plurality of combined ranging sessions is not received by another UEmore than a predetermined threshold number of times.
 51. The first UE ofclaim 41, wherein the at least one processor is further configured tosend, via the wireless transceiver, a capability message indicatingavailability of combining ranging sessions.
 52. The first UE of claim41, wherein the first UE, the second UE, and the third UE are each oneof a vehicle based UE, a pedestrian based UE, or a roadside unit.
 53. Afirst user equipment (UE) configured for ranging between UEs, the firstUE comprising: means for sending an initial message to a second UE toinitiate a first ranging session; means for receiving a message from thesecond UE to combine the first ranging session with a second rangingsession initiated by a third UE and indicating that the second UE willinitiate a combined ranging session; and means for performing thecombined ranging session with the second UE.
 54. The first UE of claim53, further comprising means for receiving an initial message from thesecond UE to initiate the combined ranging session.
 55. The first UE ofclaim 53, wherein the combined ranging session includes all UEs thatparticipated in the first ranging session and the second rangingsession, including the first UE, the second UE, the third UE, and aplurality of responder UEs.